# Rambda `Rambda` is smaller and faster alternative to the popular functional programming library **Ramda**. - [Documentation](https://selfrefactor.github.io/rambda/#/) [![CircleCI](https://circleci.com/gh/selfrefactor/rambda/tree/master.svg?style=svg)](https://circleci.com/gh/selfrefactor/rambda/tree/master) [![codecov](https://codecov.io/gh/selfrefactor/rambda/branch/master/graph/badge.svg)](https://codecov.io/gh/selfrefactor/rambda) ![Commit activity](https://img.shields.io/github/commit-activity/y/selfrefactor/rambda) ![All contributors](https://img.shields.io/github/contributors/selfrefactor/rambda) ![Library size](https://img.shields.io/bundlephobia/minzip/rambda) [![install size](https://packagephobia.com/badge?p=rambda)](https://packagephobia.com/result?p=rambda) [![nest badge](https://nest.land/badge.svg)](https://nest.land/package/rambda) [![HitCount](https://hits.dwyl.com/selfrefactor/rambda.svg?style=flat-square)](http://hits.dwyl.com/selfrefactor/rambda) ## ❯ Example use ```javascript import { compose, map, filter } from 'rambda' const result = compose( map(x => x * 2), filter(x => x > 2) )([1, 2, 3, 4]) // => [6, 8] ``` You can test this example in Rambda's REPL * [Differences between Rambda and Ramda](#differences-between-rambda-and-ramda) * [API](#api) * [Changelog](#-changelog) [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#-example-use) ## ❯ Rambda's advantages ### Typescript included Typescript definitions are included in the library, in comparison to **Ramda**, where you need to additionally install `@types/ramda`. Still, you need to be aware that functional programming features in `Typescript` are in development, which means that using **R.compose/R.pipe** can be problematic. Important - Rambda version `7.1.0`(or higher) requires Typescript version `4.3.3`(or higher). #### Immutable TS definitions You can use immutable version of Rambda definitions, which is linted with ESLint `functional/prefer-readonly-type` plugin. ``` import {add} from 'rambda/immutable' ``` ### Deno support While `Ramda` is available for `Deno` users, `Rambda` provides you with included TS definitions: ``` import * as R from "https://x.nest.land/rambda@7.1.0/mod.ts"; import * as Ramda from "https://x.nest.land/ramda@0.28.0/mod.ts"; R.add(1)('foo') // => will trigger warning in VSCode Ramda.add(1)('foo') // => will not trigger warning in VSCode ``` ### Smaller size The size of a library affects not only the build bundle size but also the dev bundle size and build time. This is important advantage, expecially for big projects. ### Dot notation for `R.path`, `R.paths`, `R.assocPath` and `R.lensPath` Standard usage of `R.path` is `R.path(['a', 'b'], {a: {b: 1} })`. In **Rambda** you have the choice to use dot notation(which is arguably more readable): ``` R.path('a.b', {a: {b: 1} }) ``` ### Comma notation for `R.pick` and `R.omit` Similar to dot notation, but the separator is comma(`,`) instead of dot(`.`). ``` R.pick('a,b', {a: 1 , b: 2, c: 3} }) // No space allowed between properties ``` ### Speed **Rambda** is generally more performant than `Ramda` as the [benchmarks](#-benchmarks) can prove that. ### Support As the library is smaller than Ramda, issues are much faster resolved. Closing the issue is usually accompanied by publishing a new patch version of `Rambda` to NPM. [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#-rambdas-advantages) ## ❯ Missing Ramda methods

Click to see the full list of 76 Ramda methods not implemented in Rambda

- __ - addIndex - ap - aperture - applyTo - ascend - binary - call - collectBy - comparator - composeWith - construct - constructN - descend - differenceWith - dissocPath - empty - eqBy - forEachObjIndexed - gt - gte - hasIn - innerJoin - insert - insertAll - into - invert - invertObj - invoker - keysIn - lift - liftN - lt - lte - mapAccum - mapAccumRight - memoizeWith - mergeDeepLeft - mergeDeepWith - mergeDeepWithKey - mergeWithKey - nAry - nthArg - o - otherwise - pair - partialRight - pathSatisfies - pickBy - pipeWith - project - promap - reduceBy - reduceRight - reduceWhile - reduced - remove - scan - sequence - sortWith - splitWhenever - symmetricDifferenceWith - andThen - toPairsIn - transduce - traverse - unary - uncurryN - unfold - unionWith - until - useWith - valuesIn - xprod - thunkify - default

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#-missing-ramda-methods) ## ❯ Install - **yarn add rambda** - For UMD usage either use `./dist/rambda.umd.js` or the following CDN link: ``` https://unpkg.com/rambda@CURRENT_VERSION/dist/rambda.umd.js ``` - with deno ``` import {compose, add} from 'https://raw.githubusercontent.com/selfrefactor/rambda/master/dist/rambda.esm.js' ``` [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#-install) ## Differences between Rambda and Ramda - Rambda's **type** detects async functions and unresolved `Promises`. The returned values are `'Async'` and `'Promise'`. - Rambda's **type** handles *NaN* input, in which case it returns `NaN`. - Rambda's **forEach** can iterate over objects not only arrays. - Rambda's **map**, **filter**, **partition** when they iterate over objects, they pass property and input object as predicate's argument. - Rambda's **filter** returns empty array with bad input(`null` or `undefined`), while Ramda throws. - Ramda's **clamp** work with strings, while Rambda's method work only with numbers. - Ramda's **indexOf/lastIndexOf** work with strings and lists, while Rambda's method work only with lists as iterable input. - Error handling, when wrong inputs are provided, may not be the same. This difference will be better documented once all brute force tests are completed. - Typescript definitions between `rambda` and `@types/ramda` may vary. > If you need more **Ramda** methods in **Rambda**, you may either submit a `PR` or check the extended version of **Rambda** - [Rambdax](https://github.com/selfrefactor/rambdax). In case of the former, you may want to consult with [Rambda contribution guidelines.](CONTRIBUTING.md) [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#-differences-between-rambda-and-ramda) ## ❯ Benchmarks

Click to expand all benchmark results There are methods which are benchmarked only with `Ramda` and `Rambda`(i.e. no `Lodash`). Note that some of these methods, are called with and without curring. This is done in order to give more detailed performance feedback. The benchmarks results are produced from latest versions of *Rambda*, *Lodash*(4.17.21) and *Ramda*(0.28.0).

method | Rambda | Ramda | Lodash --- |--- | --- | --- *add* | 🚀 Fastest | 21.52% slower | 82.15% slower *adjust* | 8.48% slower | 🚀 Fastest | 🔳 *all* | 🚀 Fastest | 1.81% slower | 🔳 *allPass* | 🚀 Fastest | 91.09% slower | 🔳 *allPass* | 🚀 Fastest | 98.56% slower | 🔳 *and* | 🚀 Fastest | 89.09% slower | 🔳 *any* | 🚀 Fastest | 92.87% slower | 45.82% slower *anyPass* | 🚀 Fastest | 98.25% slower | 🔳 *append* | 🚀 Fastest | 2.07% slower | 🔳 *applySpec* | 🚀 Fastest | 80.43% slower | 🔳 *assoc* | 72.32% slower | 60.08% slower | 🚀 Fastest *clone* | 🚀 Fastest | 91.86% slower | 86.48% slower *compose* | 🚀 Fastest | 32.45% slower | 13.68% slower *converge* | 78.63% slower | 🚀 Fastest | 🔳 *curry* | 🚀 Fastest | 28.86% slower | 🔳 *curryN* | 🚀 Fastest | 41.05% slower | 🔳 *defaultTo* | 🚀 Fastest | 48.91% slower | 🔳 *drop* | 🚀 Fastest | 82.35% slower | 🔳 *dropLast* | 🚀 Fastest | 86.74% slower | 🔳 *equals* | 58.37% slower | 96.73% slower | 🚀 Fastest *filter* | 6.7% slower | 72.03% slower | 🚀 Fastest *find* | 🚀 Fastest | 85.14% slower | 42.65% slower *findIndex* | 🚀 Fastest | 86.48% slower | 72.27% slower *flatten* | 6.56% slower | 86.64% slower | 🚀 Fastest *ifElse* | 🚀 Fastest | 58.56% slower | 🔳 *includes* | 🚀 Fastest | 84.63% slower | 🔳 *indexOf* | 🚀 Fastest | 76.63% slower | 🔳 *indexOf* | 🚀 Fastest | 82.2% slower | 🔳 *init* | 🚀 Fastest | 92.24% slower | 13.3% slower *is* | 🚀 Fastest | 57.69% slower | 🔳 *isEmpty* | 🚀 Fastest | 97.14% slower | 54.99% slower *last* | 🚀 Fastest | 93.43% slower | 5.28% slower *lastIndexOf* | 🚀 Fastest | 85.19% slower | 🔳 *map* | 🚀 Fastest | 86.6% slower | 11.73% slower *match* | 🚀 Fastest | 44.83% slower | 🔳 *merge* | 🚀 Fastest | 12.21% slower | 55.76% slower *none* | 🚀 Fastest | 96.48% slower | 🔳 *objOf* | 🚀 Fastest | 38.05% slower | 🔳 *omit* | 🚀 Fastest | 69.95% slower | 97.34% slower *over* | 🚀 Fastest | 56.23% slower | 🔳 *path* | 37.81% slower | 77.81% slower | 🚀 Fastest *pick* | 🚀 Fastest | 19.07% slower | 80.2% slower *pipe* | 0.87% slower | 🚀 Fastest | 🔳 *prop* | 🚀 Fastest | 87.95% slower | 🔳 *propEq* | 🚀 Fastest | 91.92% slower | 🔳 *range* | 🚀 Fastest | 61.8% slower | 57.44% slower *reduce* | 60.48% slower | 77.1% slower | 🚀 Fastest *repeat* | 48.57% slower | 68.98% slower | 🚀 Fastest *replace* | 33.45% slower | 33.99% slower | 🚀 Fastest *set* | 🚀 Fastest | 50.35% slower | 🔳 *sort* | 🚀 Fastest | 40.23% slower | 🔳 *sortBy* | 🚀 Fastest | 25.29% slower | 56.88% slower *split* | 🚀 Fastest | 55.37% slower | 17.64% slower *splitEvery* | 🚀 Fastest | 71.98% slower | 🔳 *take* | 🚀 Fastest | 91.96% slower | 4.72% slower *takeLast* | 🚀 Fastest | 93.39% slower | 19.22% slower *test* | 🚀 Fastest | 82.34% slower | 🔳 *type* | 🚀 Fastest | 48.6% slower | 🔳 *uniq* | 🚀 Fastest | 90.24% slower | 🔳 *uniqWith* | 18.09% slower | 🚀 Fastest | 🔳 *uniqWith* | 14.23% slower | 🚀 Fastest | 🔳 *update* | 🚀 Fastest | 52.35% slower | 🔳 *view* | 🚀 Fastest | 76.15% slower | 🔳

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#-benchmarks) ## ❯ Used by - [WatermelonDB](https://github.com/Nozbe/WatermelonDB) - [Walmart Canada](https://www.walmart.ca) reported by [w-b-dev](https://github.com/w-b-dev) - [VSCode Slack integration](https://github.com/verydanny/vcslack) - [Webpack PostCSS](https://github.com/sectsect/webpack-postcss) - [MobX-State-Tree decorators](https://github.com/farwayer/mst-decorators) - [Rewrite of the Betaflight configurator](https://github.com/freshollie/fresh-configurator) - [MineFlayer plugin](https://github.com/G07cha/MineflayerArmorManager) [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#-used-by) ## API ### add It adds `a` and `b`. Try this R.add example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#add) ### adjust ```typescript adjust(index: number, replaceFn: (x: T) => T, list: T[]): T[] ``` It replaces `index` in array `list` with the result of `replaceFn(list[i])`. Try this R.adjust example in Rambda REPL

All Typescript definitions

```typescript adjust(index: number, replaceFn: (x: T) => T, list: T[]): T[]; adjust(index: number, replaceFn: (x: T) => T): (list: T[]) => T[]; ```

R.adjust source

```javascript import { cloneList } from './_internals/cloneList.js' import { curry } from './curry.js' function adjustFn( index, replaceFn, list ){ const actualIndex = index < 0 ? list.length + index : index if (index >= list.length || actualIndex < 0) return list const clone = cloneList(list) clone[ actualIndex ] = replaceFn(clone[ actualIndex ]) return clone } export const adjust = curry(adjustFn) ```

Tests

```javascript import { add } from './add.js' import { adjust } from './adjust.js' import { pipe } from './pipe.js' const list = [ 0, 1, 2 ] const expected = [ 0, 11, 2 ] test('happy', () => {}) test('happy', () => { expect(adjust( 1, add(10), list )).toEqual(expected) }) test('with curring type 1 1 1', () => { expect(adjust(1)(add(10))(list)).toEqual(expected) }) test('with curring type 1 2', () => { expect(adjust(1)(add(10), list)).toEqual(expected) }) test('with curring type 2 1', () => { expect(adjust(1, add(10))(list)).toEqual(expected) }) test('with negative index', () => { expect(adjust( -2, add(10), list )).toEqual(expected) }) test('when index is out of bounds', () => { const list = [ 0, 1, 2, 3 ] expect(adjust( 4, add(1), list )).toEqual(list) expect(adjust( -5, add(1), list )).toEqual(list) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#adjust) ### all ```typescript all(predicate: (x: T) => boolean, list: T[]): boolean ``` It returns `true`, if all members of array `list` returns `true`, when applied as argument to `predicate` function. Try this R.all example in Rambda REPL

All Typescript definitions

```typescript all(predicate: (x: T) => boolean, list: T[]): boolean; all(predicate: (x: T) => boolean): (list: T[]) => boolean; ```

R.all source

```javascript export function all(predicate, list){ if (arguments.length === 1) return _list => all(predicate, _list) for (let i = 0; i < list.length; i++){ if (!predicate(list[ i ])) return false } return true } ```

Tests

```javascript import { all } from './all.js' const list = [ 0, 1, 2, 3, 4 ] test('when true', () => { const fn = x => x > -1 expect(all(fn)(list)).toBeTrue() }) test('when false', () => { const fn = x => x > 2 expect(all(fn, list)).toBeFalse() }) ```

Typescript test

```typescript import {all} from 'rambda' describe('all', () => { it('happy', () => { const result = all( x => { x // $ExpectType number return x > 0 }, [1, 2, 3] ) result // $ExpectType boolean }) it('curried needs a type', () => { const result = all(x => { x // $ExpectType number return x > 0 })([1, 2, 3]) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#all) ### allPass ```typescript allPass(predicates: ((x: T) => boolean)[]): (input: T) => boolean ``` It returns `true`, if all functions of `predicates` return `true`, when `input` is their argument. Try this R.allPass example in Rambda REPL

All Typescript definitions

```typescript allPass(predicates: ((x: T) => boolean)[]): (input: T) => boolean; allPass(predicates: ((...inputs: T[]) => boolean)[]): (...inputs: T[]) => boolean; ```

R.allPass source

```javascript export function allPass(predicates){ return (...input) => { let counter = 0 while (counter < predicates.length){ if (!predicates[ counter ](...input)){ return false } counter++ } return true } } ```

Tests

```javascript import { allPass } from './allPass.js' test('happy', () => { const rules = [ x => typeof x === 'number', x => x > 10, x => x * 7 < 100 ] expect(allPass(rules)(11)).toBeTrue() expect(allPass(rules)(undefined)).toBeFalse() }) test('when returns true', () => { const conditionArr = [ val => val.a === 1, val => val.b === 2 ] expect(allPass(conditionArr)({ a : 1, b : 2, })).toBeTrue() }) test('when returns false', () => { const conditionArr = [ val => val.a === 1, val => val.b === 3 ] expect(allPass(conditionArr)({ a : 1, b : 2, })).toBeFalse() }) test('works with multiple inputs', () => { const fn = function ( w, x, y, z ){ return w + x === y + z } expect(allPass([ fn ])( 3, 3, 3, 3 )).toBeTrue() }) ```

Typescript test

```typescript import {allPass, filter} from 'rambda' describe('allPass', () => { it('happy', () => { const x = allPass([ y => { y // $ExpectType number return typeof y === 'number' }, y => { return y > 0 }, ])(11) x // $ExpectType boolean }) it('issue #642', () => { const isGreater = (num: number) => num > 5 const pred = allPass([isGreater]) const xs = [0, 1, 2, 3] const filtered1 = filter(pred)(xs) filtered1 // $ExpectType number[] const filtered2 = xs.filter(pred) filtered2 // $ExpectType number[] }) it('issue #604', () => { const plusEq = function(w: number, x: number, y: number, z: number) { return w + x === y + z } const result = allPass([plusEq])(3, 3, 3, 3) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#allPass) ### always It returns function that always returns `x`. Try this R.always example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#always) ### and Logical AND Try this R.and example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#and) ### any ```typescript any(predicate: (x: T) => boolean, list: T[]): boolean ``` It returns `true`, if at least one member of `list` returns true, when passed to a `predicate` function. Try this R.any example in Rambda REPL

All Typescript definitions

```typescript any(predicate: (x: T) => boolean, list: T[]): boolean; any(predicate: (x: T) => boolean): (list: T[]) => boolean; ```

R.any source

```javascript export function any(predicate, list){ if (arguments.length === 1) return _list => any(predicate, _list) let counter = 0 while (counter < list.length){ if (predicate(list[ counter ], counter)){ return true } counter++ } return false } ```

Tests

```javascript import { any } from './any.js' const list = [ 1, 2, 3 ] test('happy', () => { expect(any(x => x < 0, list)).toBeFalse() }) test('with curry', () => { expect(any(x => x > 2)(list)).toBeTrue() }) ```

Typescript test

```typescript import {any} from 'rambda' describe('R.any', () => { it('happy', () => { const result = any( x => { x // $ExpectType number return x > 2 }, [1, 2, 3] ) result // $ExpectType boolean }) it('when curried needs a type', () => { const result = any(x => { x // $ExpectType number return x > 2 })([1, 2, 3]) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#any) ### anyPass ```typescript anyPass(predicates: ((x: T) => boolean)[]): (input: T) => boolean ``` It accepts list of `predicates` and returns a function. This function with its `input` will return `true`, if any of `predicates` returns `true` for this `input`. Try this R.anyPass example in Rambda REPL

All Typescript definitions

```typescript anyPass(predicates: ((x: T) => boolean)[]): (input: T) => boolean; anyPass(predicates: ((...inputs: T[]) => boolean)[]): (...inputs: T[]) => boolean; ```

R.anyPass source

```javascript export function anyPass(predicates){ return (...input) => { let counter = 0 while (counter < predicates.length){ if (predicates[ counter ](...input)){ return true } counter++ } return false } } ```

Tests

```javascript import { anyPass } from './anyPass.js' test('happy', () => { const rules = [ x => typeof x === 'string', x => x > 10 ] const predicate = anyPass(rules) expect(predicate('foo')).toBeTrue() expect(predicate(6)).toBeFalse() }) test('happy', () => { const rules = [ x => typeof x === 'string', x => x > 10 ] expect(anyPass(rules)(11)).toBeTrue() expect(anyPass(rules)(undefined)).toBeFalse() }) const obj = { a : 1, b : 2, } test('when returns true', () => { const conditionArr = [ val => val.a === 1, val => val.a === 2 ] expect(anyPass(conditionArr)(obj)).toBeTrue() }) test('when returns false + curry', () => { const conditionArr = [ val => val.a === 2, val => val.b === 3 ] expect(anyPass(conditionArr)(obj)).toBeFalse() }) test('with empty predicates list', () => { expect(anyPass([])(3)).toBeFalse() }) test('works with multiple inputs', () => { const fn = function ( w, x, y, z ){ console.log( w, x, y, z ) return w + x === y + z } expect(anyPass([ fn ])( 3, 3, 3, 3 )).toBeTrue() }) ```

Typescript test

```typescript import {anyPass, filter} from 'rambda' describe('anyPass', () => { it('happy', () => { const x = anyPass([ y => { y // $ExpectType number return typeof y === 'number' }, y => { return y > 0 }, ])(11) x // $ExpectType boolean }) it('issue #604', () => { const plusEq = function(w: number, x: number, y: number, z: number) { return w + x === y + z } const result = anyPass([plusEq])(3, 3, 3, 3) result // $ExpectType boolean }) it('issue #642', () => { const isGreater = (num: number) => num > 5 const pred = anyPass([isGreater]) const xs = [0, 1, 2, 3] const filtered1 = filter(pred)(xs) filtered1 // $ExpectType number[] const filtered2 = xs.filter(pred) filtered2 // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#anyPass) ### append ```typescript append(x: T, list: T[]): T[] ``` It adds element `x` at the end of `list`. Try this R.append example in Rambda REPL

All Typescript definitions

```typescript append(x: T, list: T[]): T[]; append(x: T): (list: T[]) => T[]; ```

R.append source

```javascript import { cloneList } from './_internals/cloneList.js' export function append(x, input){ if (arguments.length === 1) return _input => append(x, _input) if (typeof input === 'string') return input.split('').concat(x) const clone = cloneList(input) clone.push(x) return clone } ```

Tests

```javascript import { append } from './append.js' test('happy', () => { expect(append('tests', [ 'write', 'more' ])).toEqual([ 'write', 'more', 'tests', ]) }) test('append to empty array', () => { expect(append('tests')([])).toEqual([ 'tests' ]) }) test('with strings', () => { expect(append('o', 'fo')).toEqual([ 'f', 'o', 'o' ]) }) ```

Typescript test

```typescript import {append} from 'rambda' const list = [1, 2, 3] describe('R.append', () => { it('happy', () => { const result = append(4, list) result // $ExpectType number[] }) it('curried', () => { const result = append(4)(list) result // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#append) ### apply ```typescript apply(fn: (...args: any[]) => T, args: any[]): T ``` It applies function `fn` to the list of arguments. This is useful for creating a fixed-arity function from a variadic function. `fn` should be a bound function if context is significant. Try this R.apply example in Rambda REPL

All Typescript definitions

```typescript apply(fn: (...args: any[]) => T, args: any[]): T; apply(fn: (...args: any[]) => T): (args: any[]) => T; ```

R.apply source

```javascript export function apply(fn, args){ if (arguments.length === 1){ return _args => apply(fn, _args) } return fn.apply(this, args) } ```

Tests

```javascript import { apply } from './apply.js' import { bind } from './bind.js' import { identity } from './identity.js' test('happy', () => { expect(apply(identity, [ 1, 2, 3 ])).toBe(1) }) test('applies function to argument list', () => { expect(apply(Math.max, [ 1, 2, 3, -99, 42, 6, 7 ])).toBe(42) }) test('provides no way to specify context', () => { const obj = { method : function (){ return this === obj }, } expect(apply(obj.method, [])).toBeFalse() expect(apply(bind(obj.method, obj), [])).toBeTrue() }) ```

Typescript test

```typescript import {apply, identity} from 'rambda' describe('R.apply', () => { it('happy', () => { const result = apply(identity, [1, 2, 3]) result // $ExpectType number }) it('curried', () => { const fn = apply(identity) const result = fn([1, 2, 3]) result // $ExpectType number }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#apply) ### applySpec ```typescript applySpec>( spec: Spec ): ( ...args: Parameters> ) => { [Key in keyof Spec]: ReturnType } ``` Try this R.applySpec example in Rambda REPL

All Typescript definitions

```typescript applySpec>( spec: Spec ): ( ...args: Parameters> ) => { [Key in keyof Spec]: ReturnType }; applySpec(spec: any): (...args: unknown[]) => T; ```

R.applySpec source

```javascript import { isArray } from './_internals/isArray.js' // recursively traverse the given spec object to find the highest arity function export function __findHighestArity(spec, max = 0){ for (const key in spec){ if (spec.hasOwnProperty(key) === false || key === 'constructor') continue if (typeof spec[ key ] === 'object'){ max = Math.max(max, __findHighestArity(spec[ key ])) } if (typeof spec[ key ] === 'function'){ max = Math.max(max, spec[ key ].length) } } return max } function __filterUndefined(){ const defined = [] let i = 0 const l = arguments.length while (i < l){ if (typeof arguments[ i ] === 'undefined') break defined[ i ] = arguments[ i ] i++ } return defined } function __applySpecWithArity( spec, arity, cache ){ const remaining = arity - cache.length if (remaining === 1) return x => __applySpecWithArity( spec, arity, __filterUndefined(...cache, x) ) if (remaining === 2) return (x, y) => __applySpecWithArity( spec, arity, __filterUndefined( ...cache, x, y ) ) if (remaining === 3) return ( x, y, z ) => __applySpecWithArity( spec, arity, __filterUndefined( ...cache, x, y, z ) ) if (remaining === 4) return ( x, y, z, a ) => __applySpecWithArity( spec, arity, __filterUndefined( ...cache, x, y, z, a ) ) if (remaining > 4) return (...args) => __applySpecWithArity( spec, arity, __filterUndefined(...cache, ...args) ) // handle spec as Array if (isArray(spec)){ const ret = [] let i = 0 const l = spec.length for (; i < l; i++){ // handle recursive spec inside array if (typeof spec[ i ] === 'object' || isArray(spec[ i ])){ ret[ i ] = __applySpecWithArity( spec[ i ], arity, cache ) } // apply spec to the key if (typeof spec[ i ] === 'function'){ ret[ i ] = spec[ i ](...cache) } } return ret } // handle spec as Object const ret = {} // apply callbacks to each property in the spec object for (const key in spec){ if (spec.hasOwnProperty(key) === false || key === 'constructor') continue // apply the spec recursively if (typeof spec[ key ] === 'object'){ ret[ key ] = __applySpecWithArity( spec[ key ], arity, cache ) continue } // apply spec to the key if (typeof spec[ key ] === 'function'){ ret[ key ] = spec[ key ](...cache) } } return ret } export function applySpec(spec, ...args){ // get the highest arity spec function, cache the result and pass to __applySpecWithArity const arity = __findHighestArity(spec) if (arity === 0){ return () => ({}) } const toReturn = __applySpecWithArity( spec, arity, args ) return toReturn } ```

Tests

```javascript import { applySpec as applySpecRamda, nAry } from 'ramda' import { add, always, compose, dec, inc, map, path, prop, T, } from '../rambda.js' import { applySpec } from './applySpec.js' test('different than Ramda when bad spec', () => { const result = applySpec({ sum : { a : 1 } })(1, 2) const ramdaResult = applySpecRamda({ sum : { a : 1 } })(1, 2) expect(result).toEqual({}) expect(ramdaResult).toEqual({ sum : { a : {} } }) }) test('works with empty spec', () => { expect(applySpec({})()).toEqual({}) expect(applySpec([])(1, 2)).toEqual({}) expect(applySpec(null)(1, 2)).toEqual({}) }) test('works with unary functions', () => { const result = applySpec({ v : inc, u : dec, })(1) const expected = { v : 2, u : 0, } expect(result).toEqual(expected) }) test('works with binary functions', () => { const result = applySpec({ sum : add })(1, 2) expect(result).toEqual({ sum : 3 }) }) test('works with nested specs', () => { const result = applySpec({ unnested : always(0), nested : { sum : add }, })(1, 2) const expected = { unnested : 0, nested : { sum : 3 }, } expect(result).toEqual(expected) }) test('works with arrays of nested specs', () => { const result = applySpec({ unnested : always(0), nested : [ { sum : add } ], })(1, 2) expect(result).toEqual({ unnested : 0, nested : [ { sum : 3 } ], }) }) test('works with arrays of spec objects', () => { const result = applySpec([ { sum : add } ])(1, 2) expect(result).toEqual([ { sum : 3 } ]) }) test('works with arrays of functions', () => { const result = applySpec([ map(prop('a')), map(prop('b')) ])([ { a : 'a1', b : 'b1', }, { a : 'a2', b : 'b2', }, ]) const expected = [ [ 'a1', 'a2' ], [ 'b1', 'b2' ], ] expect(result).toEqual(expected) }) test('works with a spec defining a map key', () => { expect(applySpec({ map : prop('a') })({ a : 1 })).toEqual({ map : 1 }) }) test('cannot retains the highest arity', () => { const f = applySpec({ f1 : nAry(2, T), f2 : nAry(5, T), }) const fRamda = applySpecRamda({ f1 : nAry(2, T), f2 : nAry(5, T), }) expect(f).toHaveLength(0) expect(fRamda).toHaveLength(5) }) test('returns a curried function', () => { expect(applySpec({ sum : add })(1)(2)).toEqual({ sum : 3 }) }) // Additional tests // ============================================ test('arity', () => { const spec = { one : x1 => x1, two : (x1, x2) => x1 + x2, three : ( x1, x2, x3 ) => x1 + x2 + x3, } expect(applySpec( spec, 1, 2, 3 )).toEqual({ one : 1, two : 3, three : 6, }) }) test('arity over 5 arguments', () => { const spec = { one : x1 => x1, two : (x1, x2) => x1 + x2, three : ( x1, x2, x3 ) => x1 + x2 + x3, four : ( x1, x2, x3, x4 ) => x1 + x2 + x3 + x4, five : ( x1, x2, x3, x4, x5 ) => x1 + x2 + x3 + x4 + x5, } expect(applySpec( spec, 1, 2, 3, 4, 5 )).toEqual({ one : 1, two : 3, three : 6, four : 10, five : 15, }) }) test('curried', () => { const spec = { one : x1 => x1, two : (x1, x2) => x1 + x2, three : ( x1, x2, x3 ) => x1 + x2 + x3, } expect(applySpec(spec)(1)(2)(3)).toEqual({ one : 1, two : 3, three : 6, }) }) test('curried over 5 arguments', () => { const spec = { one : x1 => x1, two : (x1, x2) => x1 + x2, three : ( x1, x2, x3 ) => x1 + x2 + x3, four : ( x1, x2, x3, x4 ) => x1 + x2 + x3 + x4, five : ( x1, x2, x3, x4, x5 ) => x1 + x2 + x3 + x4 + x5, } expect(applySpec(spec)(1)(2)(3)(4)(5)).toEqual({ one : 1, two : 3, three : 6, four : 10, five : 15, }) }) test('undefined property', () => { const spec = { prop : path([ 'property', 'doesnt', 'exist' ]) } expect(applySpec(spec, {})).toEqual({ prop : undefined }) }) test('restructure json object', () => { const spec = { id : path('user.id'), name : path('user.firstname'), profile : path('user.profile'), doesntExist : path('user.profile.doesntExist'), info : { views : compose(inc, prop('views')) }, type : always('playa'), } const data = { user : { id : 1337, firstname : 'john', lastname : 'shaft', profile : 'shaft69', }, views : 42, } expect(applySpec(spec, data)).toEqual({ id : 1337, name : 'john', profile : 'shaft69', doesntExist : undefined, info : { views : 43 }, type : 'playa', }) }) ```

Typescript test

```typescript import {multiply, applySpec, inc, dec, add} from 'rambda' describe('applySpec', () => { it('ramda 1', () => { const result = applySpec({ v: inc, u: dec, })(1) result // $ExpectType { v: number; u: number; } }) it('ramda 1', () => { interface Output { sum: number, multiplied: number, } const result = applySpec({ sum: add, multiplied: multiply, })(1, 2) result // $ExpectType Output }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#applySpec) ### assoc It makes a shallow clone of `obj` with setting or overriding the property `prop` with `newValue`. Try this R.assoc example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#assoc) ### assocPath ```typescript assocPath(path: Path, newValue: any, obj: object): Output ``` It makes a shallow clone of `obj` with setting or overriding with `newValue` the property found with `path`. Try this R.assocPath example in Rambda REPL

All Typescript definitions

```typescript assocPath(path: Path, newValue: any, obj: object): Output; assocPath(path: Path, newValue: any): (obj: object) => Output; assocPath(path: Path): (newValue: any) => (obj: object) => Output; ```

R.assocPath source

```javascript import { cloneList } from './_internals/cloneList.js' import { isArray } from './_internals/isArray.js' import { isInteger } from './_internals/isInteger.js' import { assoc } from './assoc.js' import { curry } from './curry.js' function assocPathFn( path, newValue, input ){ const pathArrValue = typeof path === 'string' ? path.split('.').map(x => isInteger(Number(x)) ? Number(x) : x) : path if (pathArrValue.length === 0){ return newValue } const index = pathArrValue[ 0 ] if (pathArrValue.length > 1){ const condition = typeof input !== 'object' || input === null || !input.hasOwnProperty(index) const nextInput = condition ? isInteger(pathArrValue[ 1 ]) ? [] : {} : input[ index ] newValue = assocPathFn( Array.prototype.slice.call(pathArrValue, 1), newValue, nextInput ) } if (isInteger(index) && isArray(input)){ const arr = cloneList(input) arr[ index ] = newValue return arr } return assoc( index, newValue, input ) } export const assocPath = curry(assocPathFn) ```

Tests

```javascript import { assocPath } from './assocPath.js' test('string can be used as path input', () => { const testObj = { a : [ { b : 1 }, { b : 2 } ], d : 3, } const result = assocPath( 'a.0.b', 10, testObj ) const expected = { a : [ { b : 10 }, { b : 2 } ], d : 3, } expect(result).toEqual(expected) }) test('bug', () => { /* https://github.com/selfrefactor/rambda/issues/524 */ const state = {} const withDateLike = assocPath( [ 'outerProp', '2020-03-10' ], { prop : 2 }, state ) const withNumber = assocPath( [ 'outerProp', '5' ], { prop : 2 }, state ) const withDateLikeExpected = { outerProp : { '2020-03-10' : { prop : 2 } } } const withNumberExpected = { outerProp : { 5 : { prop : 2 } } } expect(withDateLike).toEqual(withDateLikeExpected) expect(withNumber).toEqual(withNumberExpected) }) test('adds a key to an empty object', () => { expect(assocPath( [ 'a' ], 1, {} )).toEqual({ a : 1 }) }) test('adds a key to a non-empty object', () => { expect(assocPath( 'b', 2, { a : 1 } )).toEqual({ a : 1, b : 2, }) }) test('adds a nested key to a non-empty object', () => { expect(assocPath( 'b.c', 2, { a : 1 } )).toEqual({ a : 1, b : { c : 2 }, }) }) test('adds a nested key to a nested non-empty object - curry case 1', () => { expect(assocPath('b.d', 3)({ a : 1, b : { c : 2 }, })).toEqual({ a : 1, b : { c : 2, d : 3, }, }) }) test('adds a key to a non-empty object - curry case 1', () => { expect(assocPath('b', 2)({ a : 1 })).toEqual({ a : 1, b : 2, }) }) test('adds a nested key to a non-empty object - curry case 1', () => { expect(assocPath('b.c', 2)({ a : 1 })).toEqual({ a : 1, b : { c : 2 }, }) }) test('adds a key to a non-empty object - curry case 2', () => { expect(assocPath('b')(2, { a : 1 })).toEqual({ a : 1, b : 2, }) }) test('adds a key to a non-empty object - curry case 3', () => { const result = assocPath('b')(2)({ a : 1 }) expect(result).toEqual({ a : 1, b : 2, }) }) test('changes an existing key', () => { expect(assocPath( 'a', 2, { a : 1 } )).toEqual({ a : 2 }) }) test('undefined is considered an empty object', () => { expect(assocPath( 'a', 1, undefined )).toEqual({ a : 1 }) }) test('null is considered an empty object', () => { expect(assocPath( 'a', 1, null )).toEqual({ a : 1 }) }) test('value can be null', () => { expect(assocPath( 'a', null, null )).toEqual({ a : null }) }) test('value can be undefined', () => { expect(assocPath( 'a', undefined, null )).toEqual({ a : undefined }) }) test('assignment is shallow', () => { expect(assocPath( 'a', { b : 2 }, { a : { c : 3 } } )).toEqual({ a : { b : 2 } }) }) test('empty array as path', () => { const result = assocPath( [], 3, { a : 1, b : 2, } ) expect(result).toBe(3) }) test('happy', () => { const expected = { foo : { bar : { baz : 42 } } } const result = assocPath( [ 'foo', 'bar', 'baz' ], 42, { foo : null } ) expect(result).toEqual(expected) }) ```

Typescript test

```typescript import {assocPath} from 'rambda' interface Output { a: number, foo: {bar: number}, } describe('R.assocPath - user must explicitly set type of output', () => { it('with array as path input', () => { const result = assocPath(['foo', 'bar'], 2, {a: 1}) result // $ExpectType Output }) it('with string as path input', () => { const result = assocPath('foo.bar', 2, {a: 1}) result // $ExpectType Output }) }) describe('R.assocPath - curried', () => { it('with array as path input', () => { const result = assocPath(['foo', 'bar'], 2)({a: 1}) result // $ExpectType Output }) it('with string as path input', () => { const result = assocPath('foo.bar', 2)({a: 1}) result // $ExpectType Output }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#assocPath) ### bind ```typescript bind(fn: F, thisObj: T): (...args: Parameters) => ReturnType ``` Creates a function that is bound to a context. Try this R.bind example in Rambda REPL

All Typescript definitions

```typescript bind(fn: F, thisObj: T): (...args: Parameters) => ReturnType; bind(fn: F): (thisObj: T) => (...args: Parameters) => ReturnType; ```

R.bind source

```javascript import { curryN } from './curryN.js' export function bind(fn, thisObj){ if (arguments.length === 1){ return _thisObj => bind(fn, _thisObj) } return curryN(fn.length, (...args) => fn.apply(thisObj, args)) } ```

Tests

```javascript import { bind } from './bind.js' function Foo(x){ this.x = x } function add(x){ return this.x + x } function Bar(x, y){ this.x = x this.y = y } Bar.prototype = new Foo() Bar.prototype.getX = function (){ return 'prototype getX' } test('returns a function', () => { expect(typeof bind(add)(Foo)).toBe('function') }) test('returns a function bound to the specified context object', () => { const f = new Foo(12) function isFoo(){ return this instanceof Foo } const isFooBound = bind(isFoo, f) expect(isFoo()).toBeFalse() expect(isFooBound()).toBeTrue() }) test('works with built-in types', () => { const abc = bind(String.prototype.toLowerCase, 'ABCDEFG') expect(typeof abc).toBe('function') expect(abc()).toBe('abcdefg') }) test('works with user-defined types', () => { const f = new Foo(12) function getX(){ return this.x } const getXFooBound = bind(getX, f) expect(getXFooBound()).toBe(12) }) test('works with plain objects', () => { const pojso = { x : 100 } function incThis(){ return this.x + 1 } const incPojso = bind(incThis, pojso) expect(typeof incPojso).toBe('function') expect(incPojso()).toBe(101) }) test('does not interfere with existing object methods', () => { const b = new Bar('a', 'b') function getX(){ return this.x } const getXBarBound = bind(getX, b) expect(b.getX()).toBe('prototype getX') expect(getXBarBound()).toBe('a') }) test('preserves arity', () => { const f0 = function (){ return 0 } const f1 = function (a){ return a } const f2 = function (a, b){ return a + b } const f3 = function ( a, b, c ){ return a + b + c } expect(bind(f0, {})).toHaveLength(0) expect(bind(f1, {})).toHaveLength(1) expect(bind(f2, {})).toHaveLength(2) expect(bind(f3, {})).toHaveLength(3) }) ```

Typescript test

```typescript import {bind} from 'rambda' class Foo {} function isFoo(this: T): boolean { return this instanceof Foo } describe('R.bind', () => { it('happy', () => { const foo = new Foo() const result = bind(isFoo, foo)() result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#bind) ### both ```typescript both(pred1: Pred, pred2: Pred): Pred ``` It returns a function with `input` argument. This function will return `true`, if both `firstCondition` and `secondCondition` return `true` when `input` is passed as their argument. Try this R.both example in Rambda REPL

All Typescript definitions

```typescript both(pred1: Pred, pred2: Pred): Pred; both(pred1: Predicate, pred2: Predicate): Predicate; both(pred1: Predicate): (pred2: Predicate) => Predicate; both(pred1: Pred): (pred2: Pred) => Pred; ```

R.both source

```javascript export function both(f, g){ if (arguments.length === 1) return _g => both(f, _g) return (...input) => f(...input) && g(...input) } ```

Tests

```javascript import { both } from './both.js' const firstFn = val => val > 0 const secondFn = val => val < 10 test('with curry', () => { expect(both(firstFn)(secondFn)(17)).toBeFalse() }) test('without curry', () => { expect(both(firstFn, secondFn)(7)).toBeTrue() }) test('with multiple inputs', () => { const between = function ( a, b, c ){ return a < b && b < c } const total20 = function ( a, b, c ){ return a + b + c === 20 } const fn = both(between, total20) expect(fn( 5, 7, 8 )).toBeTrue() }) test('skip evaluation of the second expression', () => { let effect = 'not evaluated' const F = function (){ return false } const Z = function (){ effect = 'Z got evaluated' } both(F, Z)() expect(effect).toBe('not evaluated') }) ```

Typescript test

```typescript import {both} from 'rambda' describe('R.both', () => { it('with passed type', () => { const fn = both( x => x > 1, x => x % 2 === 0 ) fn // $ExpectType Predicate const result = fn(2) // $ExpectType boolean result // $ExpectType boolean }) it('with passed type - curried', () => { const fn = both(x => x > 1)(x => x % 2 === 0) fn // $ExpectType Predicate const result = fn(2) result // $ExpectType boolean }) it('no type passed', () => { const fn = both( x => { x // $ExpectType any return x > 1 }, x => { x // $ExpectType any return x % 2 === 0 } ) const result = fn(2) result // $ExpectType boolean }) it('no type passed - curried', () => { const fn = both((x: number) => { x // $ExpectType number return x > 1 })((x: number) => { x // $ExpectType number return x % 2 === 0 }) const result = fn(2) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#both) ### chain ```typescript chain(fn: (n: T) => U[], list: T[]): U[] ``` The method is also known as `flatMap`. Try this R.chain example in Rambda REPL

All Typescript definitions

```typescript chain(fn: (n: T) => U[], list: T[]): U[]; chain(fn: (n: T) => U[]): (list: T[]) => U[]; ```

R.chain source

```javascript export function chain(fn, list){ if (arguments.length === 1){ return _list => chain(fn, _list) } return [].concat(...list.map(fn)) } ```

Tests

```javascript import { chain as chainRamda } from 'ramda' import { chain } from './chain.js' const duplicate = n => [ n, n ] test('happy', () => { const fn = x => [ x * 2 ] const list = [ 1, 2, 3 ] const result = chain(fn, list) expect(result).toEqual([ 2, 4, 6 ]) }) test('maps then flattens one level', () => { expect(chain(duplicate, [ 1, 2, 3 ])).toEqual([ 1, 1, 2, 2, 3, 3 ]) }) test('maps then flattens one level - curry', () => { expect(chain(duplicate)([ 1, 2, 3 ])).toEqual([ 1, 1, 2, 2, 3, 3 ]) }) test('flattens only one level', () => { const nest = n => [ [ n ] ] expect(chain(nest, [ 1, 2, 3 ])).toEqual([ [ 1 ], [ 2 ], [ 3 ] ]) }) test('can compose', () => { function dec(x){ return [ x - 1 ] } function times2(x){ return [ x * 2 ] } const mdouble = chain(times2) const mdec = chain(dec) expect(mdec(mdouble([ 10, 20, 30 ]))).toEqual([ 19, 39, 59 ]) }) test('@types/ramda broken test', () => { const score = { maths : 90, physics : 80, } const calculateTotal = score => { const { maths, physics } = score return maths + physics } const assocTotalToScore = (total, score) => ({ ...score, total, }) const calculateAndAssocTotalToScore = chainRamda(assocTotalToScore, calculateTotal) expect(() => calculateAndAssocTotalToScore(score)).toThrowErrorMatchingInlineSnapshot('"fn(...) is not a function"') }) ```

Typescript test

```typescript import {chain} from 'rambda' const list = [1, 2, 3] const fn = (x: number) => [`${x}`, `${x}`] describe('R.chain', () => { it('without passing type', () => { const result = chain(fn, list) result // $ExpectType string[] const curriedResult = chain(fn)(list) curriedResult // $ExpectType string[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#chain) ### clamp Restrict a number `input` to be within `min` and `max` limits. If `input` is bigger than `max`, then the result is `max`. If `input` is smaller than `min`, then the result is `min`. Try this R.clamp example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#clamp) ### clone It creates a deep copy of the `input`, which may contain (nested) Arrays and Objects, Numbers, Strings, Booleans and Dates. Try this R.clone example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#clone) ### complement It returns `inverted` version of `origin` function that accept `input` as argument. The return value of `inverted` is the negative boolean value of `origin(input)`. Try this R.complement example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#complement) ### compose It performs right-to-left function composition. Try this R.compose example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#compose) ### concat It returns a new string or array, which is the result of merging `x` and `y`. Try this R.concat example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#concat) ### cond It takes list with `conditions` and returns a new function `fn` that expects `input` as argument. This function will start evaluating the `conditions` in order to find the first winner(order of conditions matter). The winner is this condition, which left side returns `true` when `input` is its argument. Then the evaluation of the right side of the winner will be the final result. If no winner is found, then `fn` returns `undefined`. Try this R.cond example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#cond) ### converge Accepts a converging function and a list of branching functions and returns a new function. When invoked, this new function is applied to some arguments, each branching function is applied to those same arguments. The results of each branching function are passed as arguments to the converging function to produce the return value. Try this R.converge example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#converge) ### count It counts how many times `predicate` function returns `true`, when supplied with iteration of `list`. Try this R.count example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#count) ### countBy ```typescript countBy(transformFn: (x: T) => any, list: T[]): Record ``` It counts elements in a list after each instance of the input list is passed through `transformFn` function. Try this R.countBy example in Rambda REPL

All Typescript definitions

```typescript countBy(transformFn: (x: T) => any, list: T[]): Record; countBy(transformFn: (x: T) => any): (list: T[]) => Record; ```

R.countBy source

```javascript export function countBy(fn, list){ if (arguments.length === 1){ return _list => countBy(fn, _list) } const willReturn = {} list.forEach(item => { const key = fn(item) if (!willReturn[ key ]){ willReturn[ key ] = 1 } else { willReturn[ key ]++ } }) return willReturn } ```

Tests

```javascript import { countBy } from './countBy.js' const list = [ 'a', 'A', 'b', 'B', 'c', 'C' ] test('happy', () => { const result = countBy(x => x.toLowerCase(), list) expect(result).toEqual({ a : 2, b : 2, c : 2, }) }) ```

Typescript test

```typescript import {countBy} from 'rambda' const transformFn = (x: string) => x.toLowerCase() const list = ['a', 'A', 'b', 'B', 'c', 'C'] describe('R.countBy', () => { it('happy', () => { const result = countBy(transformFn, list) result // $ExpectType Record }) it('curried', () => { const result = countBy(transformFn)(list) result // $ExpectType Record }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#countBy) ### curry It expects a function as input and returns its curried version. Try this R.curry example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#curry) ### curryN It returns a curried equivalent of the provided function, with the specified arity. [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#curryN) ### dec It decrements a number. [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#dec) ### defaultTo ```typescript defaultTo(defaultValue: T, input: T | null | undefined): T ``` It returns `defaultValue`, if all of `inputArguments` are `undefined`, `null` or `NaN`. Else, it returns the first truthy `inputArguments` instance(from left to right). Try this R.defaultTo example in Rambda REPL

All Typescript definitions

```typescript defaultTo(defaultValue: T, input: T | null | undefined): T; defaultTo(defaultValue: T): (input: T | null | undefined) => T; ```

R.defaultTo source

```javascript function isFalsy(input){ return ( input === undefined || input === null || Number.isNaN(input) === true ) } export function defaultTo(defaultArgument, input){ if (arguments.length === 1){ return _input => defaultTo(defaultArgument, _input) } return isFalsy(input) ? defaultArgument : input } ```

Tests

```javascript import { defaultTo } from './defaultTo.js' test('with undefined', () => { expect(defaultTo('foo')(undefined)).toBe('foo') }) test('with null', () => { expect(defaultTo('foo')(null)).toBe('foo') }) test('with NaN', () => { expect(defaultTo('foo')(NaN)).toBe('foo') }) test('with empty string', () => { expect(defaultTo('foo', '')).toBe('') }) test('with false', () => { expect(defaultTo('foo', false)).toBeFalse() }) test('when inputArgument passes initial check', () => { expect(defaultTo('foo', 'bar')).toBe('bar') }) ```

Typescript test

```typescript import {defaultTo} from 'rambda' describe('R.defaultTo with Ramda spec', () => { it('happy', () => { const result = defaultTo('foo', '') result // $ExpectType "" | "foo" }) it('with explicit type', () => { const result = defaultTo('foo', null) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#defaultTo) ### difference ```typescript difference(a: T[], b: T[]): T[] ``` It returns the uniq set of all elements in the first list `a` not contained in the second list `b`. `R.equals` is used to determine equality. Try this R.difference example in Rambda REPL

All Typescript definitions

```typescript difference(a: T[], b: T[]): T[]; difference(a: T[]): (b: T[]) => T[]; ```

R.difference source

```javascript import { includes } from './includes.js' import { uniq } from './uniq.js' export function difference(a, b){ if (arguments.length === 1) return _b => difference(a, _b) return uniq(a).filter(aInstance => !includes(aInstance, b)) } ```

Tests

```javascript import { difference as differenceRamda } from 'ramda' import { difference } from './difference.js' test('difference', () => { const a = [ 1, 2, 3, 4 ] const b = [ 3, 4, 5, 6 ] expect(difference(a)(b)).toEqual([ 1, 2 ]) expect(difference([], [])).toEqual([]) }) test('difference with objects', () => { const a = [ { id : 1 }, { id : 2 }, { id : 3 }, { id : 4 } ] const b = [ { id : 3 }, { id : 4 }, { id : 5 }, { id : 6 } ] expect(difference(a, b)).toEqual([ { id : 1 }, { id : 2 } ]) }) test('no duplicates in first list', () => { const M2 = [ 1, 2, 3, 4, 1, 2, 3, 4 ] const N2 = [ 3, 3, 4, 4, 5, 5, 6, 6 ] expect(difference(M2, N2)).toEqual([ 1, 2 ]) }) test('should use R.equals', () => { expect(difference([ 1 ], [ 1 ])).toHaveLength(0) expect(differenceRamda([ NaN ], [ NaN ])).toHaveLength(0) }) ```

Typescript test

```typescript import {difference} from 'rambda' const list1 = [1, 2, 3] const list2 = [1, 2, 4] describe('R.difference', () => { it('happy', () => { const result = difference(list1, list2) result // $ExpectType number[] }) it('curried', () => { const result = difference(list1)(list2) result // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#difference) ### dissoc It returns a new object that does not contain property `prop`. Try this R.dissoc example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#dissoc) ### divide Try this R.divide example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#divide) ### drop ```typescript drop(howMany: number, input: T[]): T[] ``` It returns `howMany` items dropped from beginning of list or string `input`. Try this R.drop example in Rambda REPL

All Typescript definitions

```typescript drop(howMany: number, input: T[]): T[]; drop(howMany: number, input: string): string; drop(howMany: number): { (input: T[]): T[]; (input: string): string; }; ```

R.drop source

```javascript export function drop(howManyToDrop, listOrString){ if (arguments.length === 1) return _list => drop(howManyToDrop, _list) return listOrString.slice(howManyToDrop > 0 ? howManyToDrop : 0) } ```

Tests

```javascript import assert from 'assert' import { drop } from './drop.js' test('with array', () => { expect(drop(2)([ 'foo', 'bar', 'baz' ])).toEqual([ 'baz' ]) expect(drop(3, [ 'foo', 'bar', 'baz' ])).toEqual([]) expect(drop(4, [ 'foo', 'bar', 'baz' ])).toEqual([]) }) test('with string', () => { expect(drop(3, 'rambda')).toBe('bda') }) test('with non-positive count', () => { expect(drop(0, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) expect(drop(-1, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) expect(drop(-Infinity, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) }) test('should return copy', () => { const xs = [ 1, 2, 3 ] assert.notStrictEqual(drop(0, xs), xs) assert.notStrictEqual(drop(-1, xs), xs) }) ```

Typescript test

```typescript import {drop} from 'rambda' const list = [1, 2, 3, 4] const str = 'foobar' const howMany = 2 describe('R.drop - array', () => { it('happy', () => { const result = drop(howMany, list) result // $ExpectType number[] }) it('curried', () => { const result = drop(howMany)(list) result // $ExpectType number[] }) }) describe('R.drop - string', () => { it('happy', () => { const result = drop(howMany, str) result // $ExpectType string }) it('curried', () => { const result = drop(howMany)(str) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#drop) ### dropLast ```typescript dropLast(howMany: number, input: T[]): T[] ``` It returns `howMany` items dropped from the end of list or string `input`. Try this R.dropLast example in Rambda REPL

All Typescript definitions

```typescript dropLast(howMany: number, input: T[]): T[]; dropLast(howMany: number, input: string): string; dropLast(howMany: number): { (input: T[]): T[]; (input: string): string; }; ```

R.dropLast source

```javascript export function dropLast(howManyToDrop, listOrString){ if (arguments.length === 1){ return _listOrString => dropLast(howManyToDrop, _listOrString) } return howManyToDrop > 0 ? listOrString.slice(0, -howManyToDrop) : listOrString.slice() } ```

Tests

```javascript import assert from 'assert' import { dropLast } from './dropLast.js' test('with array', () => { expect(dropLast(2)([ 'foo', 'bar', 'baz' ])).toEqual([ 'foo' ]) expect(dropLast(3, [ 'foo', 'bar', 'baz' ])).toEqual([]) expect(dropLast(4, [ 'foo', 'bar', 'baz' ])).toEqual([]) }) test('with string', () => { expect(dropLast(3, 'rambda')).toBe('ram') }) test('with non-positive count', () => { expect(dropLast(0, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) expect(dropLast(-1, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) expect(dropLast(-Infinity, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) }) test('should return copy', () => { const xs = [ 1, 2, 3 ] assert.notStrictEqual(dropLast(0, xs), xs) assert.notStrictEqual(dropLast(-1, xs), xs) }) ```

Typescript test

```typescript import {dropLast} from 'rambda' const list = [1, 2, 3, 4] const str = 'foobar' const howMany = 2 describe('R.dropLast - array', () => { it('happy', () => { const result = dropLast(howMany, list) result // $ExpectType number[] }) it('curried', () => { const result = dropLast(howMany)(list) result // $ExpectType number[] }) }) describe('R.dropLast - string', () => { it('happy', () => { const result = dropLast(howMany, str) result // $ExpectType string }) it('curried', () => { const result = dropLast(howMany)(str) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#dropLast) ### dropLastWhile Try this R.dropLastWhile example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#dropLastWhile) ### dropRepeats ```typescript dropRepeats(list: T[]): T[] ``` It removes any successive duplicates according to `R.equals`. Try this R.dropRepeats example in Rambda REPL

All Typescript definitions

```typescript dropRepeats(list: T[]): T[]; ```

R.dropRepeats source

```javascript import { isArray } from './_internals/isArray.js' import { equals } from './equals.js' export function dropRepeats(list){ if (!isArray(list)){ throw new Error(`${ list } is not a list`) } const toReturn = [] list.reduce((prev, current) => { if (!equals(prev, current)){ toReturn.push(current) } return current }, undefined) return toReturn } ```

Tests

```javascript import { dropRepeats as dropRepeatsRamda } from 'ramda' import { compareCombinations } from './_internals/testUtils.js' import { add } from './add.js' import { dropRepeats } from './dropRepeats.js' const list = [ 1, 2, 2, 2, 3, 4, 4, 5, 5, 3, 2, 2, { a : 1 }, { a : 1 } ] const listClean = [ 1, 2, 3, 4, 5, 3, 2, { a : 1 } ] test('happy', () => { const result = dropRepeats(list) expect(result).toEqual(listClean) }) const possibleLists = [ [ add(1), async () => {}, [ 1 ], [ 1 ], [ 2 ], [ 2 ] ], [ add(1), add(1), add(2) ], [], 1, /foo/g, Promise.resolve(1), ] describe('brute force', () => { compareCombinations({ firstInput : possibleLists, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 0, "RESULTS_MISMATCH": 1, "SHOULD_NOT_THROW": 3, "SHOULD_THROW": 0, "TOTAL_TESTS": 6, } `) }, fn : dropRepeats, fnRamda : dropRepeatsRamda, }) }) ```

Typescript test

```typescript import {dropRepeats} from 'rambda' describe('R.dropRepeats', () => { it('happy', () => { const result = dropRepeats([1, 2, 2, 3]) result // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#dropRepeats) ### dropRepeatsWith Try this R.dropRepeatsWith example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#dropRepeatsWith) ### dropWhile Try this R.dropWhile example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#dropWhile) ### either ```typescript either(firstPredicate: Pred, secondPredicate: Pred): Pred ``` It returns a new `predicate` function from `firstPredicate` and `secondPredicate` inputs. This `predicate` function will return `true`, if any of the two input predicates return `true`. Try this R.either example in Rambda REPL

All Typescript definitions

```typescript either(firstPredicate: Pred, secondPredicate: Pred): Pred; either(firstPredicate: Predicate, secondPredicate: Predicate): Predicate; either(firstPredicate: Predicate): (secondPredicate: Predicate) => Predicate; either(firstPredicate: Pred): (secondPredicate: Pred) => Pred; ```

R.either source

```javascript export function either(firstPredicate, secondPredicate){ if (arguments.length === 1){ return _secondPredicate => either(firstPredicate, _secondPredicate) } return (...input) => Boolean(firstPredicate(...input) || secondPredicate(...input)) } ```

Tests

```javascript import { either } from './either.js' test('with multiple inputs', () => { const between = function ( a, b, c ){ return a < b && b < c } const total20 = function ( a, b, c ){ return a + b + c === 20 } const fn = either(between, total20) expect(fn( 7, 8, 5 )).toBeTrue() }) test('skip evaluation of the second expression', () => { let effect = 'not evaluated' const F = function (){ return true } const Z = function (){ effect = 'Z got evaluated' } either(F, Z)() expect(effect).toBe('not evaluated') }) test('case 1', () => { const firstFn = val => val > 0 const secondFn = val => val * 5 > 10 expect(either(firstFn, secondFn)(1)).toBeTrue() }) test('case 2', () => { const firstFn = val => val > 0 const secondFn = val => val === -10 const fn = either(firstFn)(secondFn) expect(fn(-10)).toBeTrue() }) ```

Typescript test

```typescript import {either} from 'rambda' describe('R.either', () => { it('with passed type', () => { const fn = either( x => x > 1, x => x % 2 === 0 ) fn // $ExpectType Predicate const result = fn(2) // $ExpectType boolean result // $ExpectType boolean }) it('with passed type - curried', () => { const fn = either(x => x > 1)(x => x % 2 === 0) fn // $ExpectType Predicate const result = fn(2) result // $ExpectType boolean }) it('no type passed', () => { const fn = either( x => { x // $ExpectType any return x > 1 }, x => { x // $ExpectType any return x % 2 === 0 } ) const result = fn(2) result // $ExpectType boolean }) it('no type passed - curried', () => { const fn = either((x: number) => { x // $ExpectType number return x > 1 })((x: number) => { x // $ExpectType number return x % 2 === 0 }) const result = fn(2) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#either) ### endsWith ```typescript endsWith(target: string, iterable: string): boolean ``` When iterable is a string, then it behaves as `String.prototype.endsWith`. When iterable is a list, then it uses R.equals to determine if the target list ends in the same way as the given target. Try this R.endsWith example in Rambda REPL

All Typescript definitions

```typescript endsWith(target: string, iterable: string): boolean; endsWith(target: string): (iterable: string) => boolean; endsWith(target: T[], list: T[]): boolean; endsWith(target: T[]): (list: T[]) => boolean; ```

R.endsWith source

```javascript import { isArray } from './_internals/isArray.js' import { equals } from './equals.js' export function endsWith(target, iterable){ if (arguments.length === 1) return _iterable => endsWith(target, _iterable) if (typeof iterable === 'string'){ return iterable.endsWith(target) } if (!isArray(target)) return false const diff = iterable.length - target.length let correct = true const filtered = target.filter((x, index) => { if (!correct) return false const result = equals(x, iterable[ index + diff ]) if (!result) correct = false return result }) return filtered.length === target.length } ```

Tests

```javascript import { endsWith as endsWithRamda } from 'ramda' import { compareCombinations } from './_internals/testUtils.js' import { endsWith } from './endsWith.js' test('with string', () => { expect(endsWith('bar', 'foo-bar')).toBeTrue() expect(endsWith('baz')('foo-bar')).toBeFalse() }) test('use R.equals with array', () => { const list = [ { a : 1 }, { a : 2 }, { a : 3 } ] expect(endsWith({ a : 3 }, list)).toBeFalse(), expect(endsWith([ { a : 3 } ], list)).toBeTrue() expect(endsWith([ { a : 2 }, { a : 3 } ], list)).toBeTrue() expect(endsWith(list, list)).toBeTrue() expect(endsWith([ { a : 1 } ], list)).toBeFalse() }) export const possibleTargets = [ NaN, [ NaN ], /foo/, [ /foo/ ], Promise.resolve(1), [ Promise.resolve(1) ], Error('foo'), [ Error('foo') ], ] export const possibleIterables = [ [ Promise.resolve(1), Promise.resolve(2) ], [ /foo/, /bar/ ], [ NaN ], [ Error('foo'), Error('bar') ], ] describe('brute force', () => { compareCombinations({ fn : endsWith, fnRamda : endsWithRamda, firstInput : possibleTargets, secondInput : possibleIterables, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 0, "RESULTS_MISMATCH": 0, "SHOULD_NOT_THROW": 0, "SHOULD_THROW": 0, "TOTAL_TESTS": 32, } `) }, }) }) ```

Typescript test

```typescript import {endsWith} from 'rambda' describe('R.endsWith - array as iterable', () => { const target = [{a: 2}] const iterable = [{a: 1}, {a: 2}] it('happy', () => { const result = endsWith(target, iterable) result // $ExpectType boolean }) it('curried', () => { const result = endsWith(target)(iterable) result // $ExpectType boolean }) }) describe('R.endsWith - string as iterable', () => { const target = 'bar' const iterable = 'foo bar' it('happy', () => { const result = endsWith(target, iterable) result // $ExpectType boolean }) it('curried', () => { const result = endsWith(target)(iterable) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#endsWith) ### eqProps It returns `true` if property `prop` in `obj1` is equal to property `prop` in `obj2` according to `R.equals`. Try this R.eqProps example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#eqProps) ### equals ```typescript equals(x: T, y: T): boolean ``` It deeply compares `x` and `y` and returns `true` if they are equal. Try this R.equals example in Rambda REPL

All Typescript definitions

```typescript equals(x: T, y: T): boolean; equals(x: T): (y: T) => boolean; ```

R.equals source

```javascript import { isArray } from './_internals/isArray.js' import { type } from './type.js' export function _lastIndexOf(valueToFind, list){ if (!isArray(list)){ throw new Error(`Cannot read property 'indexOf' of ${ list }`) } const typeOfValue = type(valueToFind) if (![ 'Object', 'Array', 'NaN', 'RegExp' ].includes(typeOfValue)) return list.lastIndexOf(valueToFind) const { length } = list let index = length let foundIndex = -1 while (--index > -1 && foundIndex === -1){ if (equals(list[ index ], valueToFind)){ foundIndex = index } } return foundIndex } export function _indexOf(valueToFind, list){ if (!isArray(list)){ throw new Error(`Cannot read property 'indexOf' of ${ list }`) } const typeOfValue = type(valueToFind) if (![ 'Object', 'Array', 'NaN', 'RegExp' ].includes(typeOfValue)) return list.indexOf(valueToFind) let index = -1 let foundIndex = -1 const { length } = list while (++index < length && foundIndex === -1){ if (equals(list[ index ], valueToFind)){ foundIndex = index } } return foundIndex } function _arrayFromIterator(iter){ const list = [] let next while (!(next = iter.next()).done){ list.push(next.value) } return list } function _equalsSets(a, b){ if (a.size !== b.size){ return false } const aList = _arrayFromIterator(a.values()) const bList = _arrayFromIterator(b.values()) const filtered = aList.filter(aInstance => _indexOf(aInstance, bList) === -1) return filtered.length === 0 } function parseError(maybeError){ const typeofError = maybeError.__proto__.toString() if (![ 'Error', 'TypeError' ].includes(typeofError)) return [] return [ typeofError, maybeError.message ] } function parseDate(maybeDate){ if (!maybeDate.toDateString) return [ false ] return [ true, maybeDate.getTime() ] } function parseRegex(maybeRegex){ if (maybeRegex.constructor !== RegExp) return [ false ] return [ true, maybeRegex.toString() ] } export function equals(a, b){ if (arguments.length === 1) return _b => equals(a, _b) const aType = type(a) if (aType !== type(b)) return false if (aType === 'Function'){ return a.name === undefined ? false : a.name === b.name } if ([ 'NaN', 'Undefined', 'Null' ].includes(aType)) return true if (aType === 'Number'){ if (Object.is(-0, a) !== Object.is(-0, b)) return false return a.toString() === b.toString() } if ([ 'String', 'Boolean' ].includes(aType)){ return a.toString() === b.toString() } if (aType === 'Array'){ const aClone = Array.from(a) const bClone = Array.from(b) if (aClone.toString() !== bClone.toString()){ return false } let loopArrayFlag = true aClone.forEach((aCloneInstance, aCloneIndex) => { if (loopArrayFlag){ if ( aCloneInstance !== bClone[ aCloneIndex ] && !equals(aCloneInstance, bClone[ aCloneIndex ]) ){ loopArrayFlag = false } } }) return loopArrayFlag } const aRegex = parseRegex(a) const bRegex = parseRegex(b) if (aRegex[ 0 ]){ return bRegex[ 0 ] ? aRegex[ 1 ] === bRegex[ 1 ] : false } else if (bRegex[ 0 ]) return false const aDate = parseDate(a) const bDate = parseDate(b) if (aDate[ 0 ]){ return bDate[ 0 ] ? aDate[ 1 ] === bDate[ 1 ] : false } else if (bDate[ 0 ]) return false const aError = parseError(a) const bError = parseError(b) if (aError[ 0 ]){ return bError[ 0 ] ? aError[ 0 ] === bError[ 0 ] && aError[ 1 ] === bError[ 1 ] : false } if (aType === 'Set'){ return _equalsSets(a, b) } if (aType === 'Object'){ const aKeys = Object.keys(a) if (aKeys.length !== Object.keys(b).length){ return false } let loopObjectFlag = true aKeys.forEach(aKeyInstance => { if (loopObjectFlag){ const aValue = a[ aKeyInstance ] const bValue = b[ aKeyInstance ] if (aValue !== bValue && !equals(aValue, bValue)){ loopObjectFlag = false } } }) return loopObjectFlag } return false } ```

Tests

```javascript import { equals as equalsRamda } from 'ramda' import { compareCombinations } from './_internals/testUtils.js' import { variousTypes } from './benchmarks/_utils.js' import { equals } from './equals.js' test('compare functions', () => { function foo(){} function bar(){} const baz = () => {} const expectTrue = equals(foo, foo) const expectFalseFirst = equals(foo, bar) const expectFalseSecond = equals(foo, baz) expect(expectTrue).toBeTrue() expect(expectFalseFirst).toBeFalse() expect(expectFalseSecond).toBeFalse() }) test('with array of objects', () => { const list1 = [ { a : 1 }, [ { b : 2 } ] ] const list2 = [ { a : 1 }, [ { b : 2 } ] ] const list3 = [ { a : 1 }, [ { b : 3 } ] ] expect(equals(list1, list2)).toBeTrue() expect(equals(list1, list3)).toBeFalse() }) test('with regex', () => { expect(equals(/s/, /s/)).toBeTrue() expect(equals(/s/, /d/)).toBeFalse() expect(equals(/a/gi, /a/gi)).toBeTrue() expect(equals(/a/gim, /a/gim)).toBeTrue() expect(equals(/a/gi, /a/i)).toBeFalse() }) test('not a number', () => { expect(equals([ NaN ], [ NaN ])).toBeTrue() }) test('new number', () => { expect(equals(new Number(0), new Number(0))).toBeTrue() expect(equals(new Number(0), new Number(1))).toBeFalse() expect(equals(new Number(1), new Number(0))).toBeFalse() }) test('new string', () => { expect(equals(new String(''), new String(''))).toBeTrue() expect(equals(new String(''), new String('x'))).toBeFalse() expect(equals(new String('x'), new String(''))).toBeFalse() expect(equals(new String('foo'), new String('foo'))).toBeTrue() expect(equals(new String('foo'), new String('bar'))).toBeFalse() expect(equals(new String('bar'), new String('foo'))).toBeFalse() }) test('new Boolean', () => { expect(equals(new Boolean(true), new Boolean(true))).toBeTrue() expect(equals(new Boolean(false), new Boolean(false))).toBeTrue() expect(equals(new Boolean(true), new Boolean(false))).toBeFalse() expect(equals(new Boolean(false), new Boolean(true))).toBeFalse() }) test('new Error', () => { expect(equals(new Error('XXX'), {})).toBeFalse() expect(equals(new Error('XXX'), new TypeError('XXX'))).toBeFalse() expect(equals(new Error('XXX'), new Error('YYY'))).toBeFalse() expect(equals(new Error('XXX'), new Error('XXX'))).toBeTrue() expect(equals(new Error('XXX'), new TypeError('YYY'))).toBeFalse() }) test('with dates', () => { expect(equals(new Date(0), new Date(0))).toBeTrue() expect(equals(new Date(1), new Date(1))).toBeTrue() expect(equals(new Date(0), new Date(1))).toBeFalse() expect(equals(new Date(1), new Date(0))).toBeFalse() expect(equals(new Date(0), {})).toBeFalse() expect(equals({}, new Date(0))).toBeFalse() }) test('ramda spec', () => { expect(equals({}, {})).toBeTrue() expect(equals({ a : 1, b : 2, }, { a : 1, b : 2, })).toBeTrue() expect(equals({ a : 2, b : 3, }, { b : 3, a : 2, })).toBeTrue() expect(equals({ a : 2, b : 3, }, { a : 3, b : 3, })).toBeFalse() expect(equals({ a : 2, b : 3, c : 1, }, { a : 2, b : 3, })).toBeFalse() }) test('works with boolean tuple', () => { expect(equals([ true, false ], [ true, false ])).toBeTrue() expect(equals([ true, false ], [ true, true ])).toBeFalse() }) test('works with equal objects within array', () => { const objFirst = { a : { b : 1, c : 2, d : [ 1 ], }, } const objSecond = { a : { b : 1, c : 2, d : [ 1 ], }, } const x = [ 1, 2, objFirst, null, '', [] ] const y = [ 1, 2, objSecond, null, '', [] ] expect(equals(x, y)).toBeTrue() }) test('works with different objects within array', () => { const objFirst = { a : { b : 1 } } const objSecond = { a : { b : 2 } } const x = [ 1, 2, objFirst, null, '', [] ] const y = [ 1, 2, objSecond, null, '', [] ] expect(equals(x, y)).toBeFalse() }) test('works with undefined as second argument', () => { expect(equals(1, undefined)).toBeFalse() expect(equals(undefined, undefined)).toBeTrue() }) test('compare sets', () => { const toCompareDifferent = new Set([ { a : 1 }, { a : 2 } ]) const toCompareSame = new Set([ { a : 1 }, { a : 2 }, { a : 1 } ]) const testSet = new Set([ { a : 1 }, { a : 2 }, { a : 1 } ]) expect(equals(toCompareSame, testSet)).toBeTruthy() expect(equals(toCompareDifferent, testSet)).toBeFalsy() expect(equalsRamda(toCompareSame, testSet)).toBeTruthy() expect(equalsRamda(toCompareDifferent, testSet)).toBeFalsy() }) test('compare simple sets', () => { const testSet = new Set([ '2', '3', '3', '2', '1' ]) expect(equals(new Set([ '3', '2', '1' ]), testSet)).toBeTruthy() expect(equals(new Set([ '3', '2', '0' ]), testSet)).toBeFalsy() }) test('various examples', () => { expect(equals([ 1, 2, 3 ])([ 1, 2, 3 ])).toBeTrue() expect(equals([ 1, 2, 3 ], [ 1, 2 ])).toBeFalse() expect(equals(1, 1)).toBeTrue() expect(equals(1, '1')).toBeFalse() expect(equals({}, {})).toBeTrue() expect(equals({ a : 1, b : 2, }, { b : 2, a : 1, })).toBeTrue() expect(equals({ a : 1, b : 2, }, { a : 1, b : 1, })).toBeFalse() expect(equals({ a : 1, b : false, }, { a : 1, b : 1, })).toBeFalse() expect(equals({ a : 1, b : 2, }, { b : 2, a : 1, c : 3, })).toBeFalse() expect(equals({ x : { a : 1, b : 2, }, }, { x : { b : 2, a : 1, c : 3, }, })).toBeFalse() expect(equals({ a : 1, b : 2, }, { b : 3, a : 1, })).toBeFalse() expect(equals({ a : { b : { c : 1 } } }, { a : { b : { c : 1 } } })).toBeTrue() expect(equals({ a : { b : { c : 1 } } }, { a : { b : { c : 2 } } })).toBeFalse() expect(equals({ a : {} }, { a : {} })).toBeTrue() expect(equals('', '')).toBeTrue() expect(equals('foo', 'foo')).toBeTrue() expect(equals('foo', 'bar')).toBeFalse() expect(equals(0, false)).toBeFalse() expect(equals(/\s/g, null)).toBeFalse() expect(equals(null, null)).toBeTrue() expect(equals(false)(null)).toBeFalse() }) test('with custom functions', () => { function foo(){ return 1 } foo.prototype.toString = () => '' const result = equals(foo, foo) expect(result).toBeTrue() }) test('with classes', () => { class Foo{} const foo = new Foo() const result = equals(foo, foo) expect(result).toBeTrue() }) test('with negative zero', () => { expect(equals(-0, -0)).toBeTrue() expect(equals(-0, 0)).toBeFalse() expect(equals(0, 0)).toBeTrue() expect(equals(-0, 1)).toBeFalse() }) const possibleInputs = variousTypes describe('brute force', () => { compareCombinations({ fn : equals, fnRamda : equalsRamda, firstInput : possibleInputs, secondInput : possibleInputs, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 0, "RESULTS_MISMATCH": 5, "SHOULD_NOT_THROW": 4, "SHOULD_THROW": 0, "TOTAL_TESTS": 289, } `) }, }) }) ```

Typescript test

```typescript import {equals} from 'rambda' describe('R.equals', () => { it('happy', () => { const result = equals(4, 1) result // $ExpectType boolean }) it('with object', () => { const foo = {a: 1} const bar = {a: 2} const result = equals(foo, bar) result // $ExpectType boolean }) it('curried', () => { const result = equals(4)(1) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#equals) ### evolve ```typescript evolve(rules: ((x: T) => U)[], list: T[]): U[] ``` It takes object or array of functions as set of rules. These `rules` are applied to the `iterable` input to produce the result. Try this R.evolve example in Rambda REPL

All Typescript definitions

```typescript evolve(rules: ((x: T) => U)[], list: T[]): U[]; evolve(rules: ((x: T) => U)[]) : (list: T[]) => U[]; evolve>(rules: E, obj: V): Evolve; evolve(rules: E): >(obj: V) => Evolve; ```

R.evolve source

```javascript import { isArray } from './_internals/isArray.js' import { mapArray, mapObject } from './map.js' import { type } from './type.js' export function evolveArray(rules, list){ return mapArray( (x, i) => { if (type(rules[ i ]) === 'Function'){ return rules[ i ](x) } return x }, list, true ) } export function evolveObject(rules, iterable){ return mapObject((x, prop) => { if (type(x) === 'Object'){ const typeRule = type(rules[ prop ]) if (typeRule === 'Function'){ return rules[ prop ](x) } if (typeRule === 'Object'){ return evolve(rules[ prop ], x) } return x } if (type(rules[ prop ]) === 'Function'){ return rules[ prop ](x) } return x }, iterable) } export function evolve(rules, iterable){ if (arguments.length === 1){ return _iterable => evolve(rules, _iterable) } const rulesType = type(rules) const iterableType = type(iterable) if (iterableType !== rulesType){ throw new Error('iterableType !== rulesType') } if (![ 'Object', 'Array' ].includes(rulesType)){ throw new Error(`'iterable' and 'rules' are from wrong type ${ rulesType }`) } if (iterableType === 'Object'){ return evolveObject(rules, iterable) } return evolveArray(rules, iterable) } ```

Tests

```javascript import { evolve as evolveRamda } from 'ramda' import { add } from '../rambda.js' import { compareCombinations, compareToRamda } from './_internals/testUtils.js' import { evolve } from './evolve.js' test('happy', () => { const rules = { foo : add(1), nested : { bar : x => Object.keys(x).length }, } const input = { a : 1, foo : 2, nested : { bar : { z : 3 } }, } const result = evolve(rules, input) expect(result).toEqual({ a : 1, foo : 3, nested : { bar : 1 }, }) }) test('nested rule is wrong', () => { const rules = { foo : add(1), nested : { bar : 10 }, } const input = { a : 1, foo : 2, nested : { bar : { z : 3 } }, } const result = evolve(rules)(input) expect(result).toEqual({ a : 1, foo : 3, nested : { bar : { z : 3 } }, }) }) test('is recursive', () => { const rules = { nested : { second : add(-1), third : add(1), }, } const object = { first : 1, nested : { second : 2, third : 3, }, } const expected = { first : 1, nested : { second : 1, third : 4, }, } const result = evolve(rules, object) expect(result).toEqual(expected) }) test('ignores primitive values', () => { const rules = { n : 2, m : 'foo', } const object = { n : 0, m : 1, } const expected = { n : 0, m : 1, } const result = evolve(rules, object) expect(result).toEqual(expected) }) test('with array', () => { const rules = [ add(1), add(-1) ] const list = [ 100, 1400 ] const expected = [ 101, 1399 ] const result = evolve(rules, list) expect(result).toEqual(expected) }) const rulesObject = { a : add(1) } const rulesList = [ add(1) ] const possibleIterables = [ null, undefined, '', 42, [], [ 1 ], { a : 1 } ] const possibleRules = [ ...possibleIterables, rulesList, rulesObject ] describe('brute force', () => { compareCombinations({ firstInput : possibleRules, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 4, "RESULTS_MISMATCH": 0, "SHOULD_NOT_THROW": 51, "SHOULD_THROW": 0, "TOTAL_TESTS": 63, } `) }, secondInput : possibleIterables, fn : evolve, fnRamda : evolveRamda, }) }) ```

Typescript test

```typescript import {evolve, add} from 'rambda' describe('R.evolve', () => { it('happy', () => { const input = { foo: 2, nested: { a: 1, bar: 3, }, } const rules = { foo: add(1), nested: { a: add(-1), bar: add(1), }, } const result = evolve(rules, input) const curriedResult = evolve(rules)(input) result.nested.a // $ExpectType number curriedResult.nested.a // $ExpectType number result.nested.bar // $ExpectType number result.foo // $ExpectType number }) it('with array', () => { const rules = [String, String] const input = [100, 1400] const result = evolve(rules, input) const curriedResult = evolve(rules)(input) result // $ExpectType string[] curriedResult // $ExpectType string[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#evolve) ### F ```typescript F(): boolean ``` Try this R.F example in Rambda REPL

All Typescript definitions

```typescript F(): boolean; ```

R.F source

```javascript export function F(){ return false } ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#F) ### filter ```typescript filter(predicate: Predicate): (input: T[]) => T[] ``` It filters list or object `input` using a `predicate` function. Try this R.filter example in Rambda REPL

All Typescript definitions

```typescript filter(predicate: Predicate): (input: T[]) => T[]; filter(predicate: Predicate, input: T[]): T[]; filter(predicate: ObjectPredicate): (x: Dictionary) => Dictionary; filter(predicate: ObjectPredicate, x: Dictionary): Dictionary; ```

R.filter source

```javascript import { isArray } from './_internals/isArray.js' export function filterObject(predicate, obj){ const willReturn = {} for (const prop in obj){ if (predicate( obj[ prop ], prop, obj )){ willReturn[ prop ] = obj[ prop ] } } return willReturn } export function filterArray( predicate, list, indexed = false ){ let index = 0 const len = list.length const willReturn = [] while (index < len){ const predicateResult = indexed ? predicate(list[ index ], index) : predicate(list[ index ]) if (predicateResult){ willReturn.push(list[ index ]) } index++ } return willReturn } export function filter(predicate, iterable){ if (arguments.length === 1) return _iterable => filter(predicate, _iterable) if (!iterable){ throw new Error('Incorrect iterable input') } if (isArray(iterable)) return filterArray( predicate, iterable, false ) return filterObject(predicate, iterable) } ```

Tests

```javascript import { filter as filterRamda } from 'ramda' import { filter } from './filter.js' import { T } from './T.js' const sampleObject = { a : 1, b : 2, c : 3, d : 4, } test('happy', () => { const isEven = n => n % 2 === 0 expect(filter(isEven, [ 1, 2, 3, 4 ])).toEqual([ 2, 4 ]) expect(filter(isEven, { a : 1, b : 2, d : 3, })).toEqual({ b : 2 }) }) test('predicate when input is object', () => { const obj = { a : 1, b : 2, } const predicate = ( val, prop, inputObject ) => { expect(inputObject).toEqual(obj) expect(typeof prop).toBe('string') return val < 2 } expect(filter(predicate, obj)).toEqual({ a : 1 }) }) test('with object', () => { const isEven = n => n % 2 === 0 const result = filter(isEven, sampleObject) const expectedResult = { b : 2, d : 4, } expect(result).toEqual(expectedResult) }) test('bad inputs difference between Ramda and Rambda', () => { expect(() => filter(T, null)).toThrowWithMessage(Error, 'Incorrect iterable input') expect(() => filter(T)(undefined)).toThrowWithMessage(Error, 'Incorrect iterable input') expect(() => filterRamda(T, null)).toThrowWithMessage(TypeError, 'Cannot read properties of null (reading \'fantasy-land/filter\')') expect(() => filterRamda(T, undefined)).toThrowWithMessage(TypeError, 'Cannot read properties of undefined (reading \'fantasy-land/filter\')') }) ```

Typescript test

```typescript import {filter} from 'rambda' const list = [1, 2, 3] const obj = {a: 1, b: 2} describe('R.filter with array', () => { it('happy', () => { const result = filter(x => { x // $ExpectType number return x > 1 }, list) result // $ExpectType number[] }) it('curried', () => { const result = filter(x => { x // $ExpectType number return x > 1 })(list) result // $ExpectType number[] }) }) describe('R.filter with objects', () => { it('happy', () => { const result = filter((val, prop, origin) => { val // $ExpectType number prop // $ExpectType string origin // $ExpectType Dictionary return val > 1 }, obj) result // $ExpectType Dictionary }) it('curried version requires second dummy type', () => { const result = filter((val, prop, origin) => { val // $ExpectType number prop // $ExpectType string origin // $ExpectType Dictionary return val > 1 })(obj) result // $ExpectType Dictionary }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#filter) ### find ```typescript find(predicate: (x: T) => boolean, list: T[]): T | undefined ``` It returns the first element of `list` that satisfy the `predicate`. If there is no such element, it returns `undefined`. Try this R.find example in Rambda REPL

All Typescript definitions

```typescript find(predicate: (x: T) => boolean, list: T[]): T | undefined; find(predicate: (x: T) => boolean): (list: T[]) => T | undefined; ```

R.find source

```javascript export function find(predicate, list){ if (arguments.length === 1) return _list => find(predicate, _list) let index = 0 const len = list.length while (index < len){ const x = list[ index ] if (predicate(x)){ return x } index++ } } ```

Tests

```javascript import { find } from './find.js' import { propEq } from './propEq.js' const list = [ { a : 1 }, { a : 2 }, { a : 3 } ] test('happy', () => { const fn = propEq('a', 2) expect(find(fn, list)).toEqual({ a : 2 }) }) test('with curry', () => { const fn = propEq('a', 4) expect(find(fn)(list)).toBeUndefined() }) test('with empty list', () => { expect(find(() => true, [])).toBeUndefined() }) ```

Typescript test

```typescript import {find} from 'rambda' const list = [1, 2, 3] describe('R.find', () => { it('happy', () => { const predicate = (x: number) => x > 2 const result = find(predicate, list) result // $ExpectType number | undefined }) it('curried', () => { const predicate = (x: number) => x > 2 const result = find(predicate)(list) result // $ExpectType number | undefined }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#find) ### findIndex ```typescript findIndex(predicate: (x: T) => boolean, list: T[]): number ``` It returns the index of the first element of `list` satisfying the `predicate` function. If there is no such element, then `-1` is returned. Try this R.findIndex example in Rambda REPL

All Typescript definitions

```typescript findIndex(predicate: (x: T) => boolean, list: T[]): number; findIndex(predicate: (x: T) => boolean): (list: T[]) => number; ```

R.findIndex source

```javascript export function findIndex(predicate, list){ if (arguments.length === 1) return _list => findIndex(predicate, _list) const len = list.length let index = -1 while (++index < len){ if (predicate(list[ index ])){ return index } } return -1 } ```

Tests

```javascript import { findIndex } from './findIndex.js' import { propEq } from './propEq.js' const list = [ { a : 1 }, { a : 2 }, { a : 3 } ] test('happy', () => { expect(findIndex(propEq('a', 2), list)).toBe(1) expect(findIndex(propEq('a', 1))(list)).toBe(0) expect(findIndex(propEq('a', 4))(list)).toEqual(-1) }) ```

Typescript test

```typescript import {findIndex} from 'rambda' const list = [1, 2, 3] describe('R.findIndex', () => { it('happy', () => { const predicate = (x: number) => x > 2 const result = findIndex(predicate, list) result // $ExpectType number }) it('curried', () => { const predicate = (x: number) => x > 2 const result = findIndex(predicate)(list) result // $ExpectType number }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#findIndex) ### findLast ```typescript findLast(fn: (x: T) => boolean, list: T[]): T | undefined ``` It returns the last element of `list` satisfying the `predicate` function. If there is no such element, then `undefined` is returned. Try this R.findLast example in Rambda REPL

All Typescript definitions

```typescript findLast(fn: (x: T) => boolean, list: T[]): T | undefined; findLast(fn: (x: T) => boolean): (list: T[]) => T | undefined; ```

R.findLast source

```javascript export function findLast(predicate, list){ if (arguments.length === 1) return _list => findLast(predicate, _list) let index = list.length while (--index >= 0){ if (predicate(list[ index ])){ return list[ index ] } } return undefined } ```

Tests

```javascript import { findLast } from './findLast.js' test('happy', () => { const result = findLast(x => x > 1, [ 1, 1, 1, 2, 3, 4, 1 ]) expect(result).toBe(4) expect(findLast(x => x === 0, [ 0, 1, 1, 2, 3, 4, 1 ])).toBe(0) }) test('with curry', () => { expect(findLast(x => x > 1)([ 1, 1, 1, 2, 3, 4, 1 ])).toBe(4) }) const obj1 = { x : 100 } const obj2 = { x : 200 } const a = [ 11, 10, 9, 'cow', obj1, 8, 7, 100, 200, 300, obj2, 4, 3, 2, 1, 0 ] const even = function (x){ return x % 2 === 0 } const gt100 = function (x){ return x > 100 } const isStr = function (x){ return typeof x === 'string' } const xGt100 = function (o){ return o && o.x > 100 } test('ramda 1', () => { expect(findLast(even, a)).toBe(0) expect(findLast(gt100, a)).toBe(300) expect(findLast(isStr, a)).toBe('cow') expect(findLast(xGt100, a)).toEqual(obj2) }) test('ramda 2', () => { expect(findLast(even, [ 'zing' ])).toBeUndefined() }) test('ramda 3', () => { expect(findLast(even, [ 2, 3, 5 ])).toBe(2) }) test('ramda 4', () => { expect(findLast(even, [])).toBeUndefined() }) ```

Typescript test

```typescript import {findLast} from 'rambda' const list = [1, 2, 3] describe('R.findLast', () => { it('happy', () => { const predicate = (x: number) => x > 2 const result = findLast(predicate, list) result // $ExpectType number | undefined }) it('curried', () => { const predicate = (x: number) => x > 2 const result = findLast(predicate)(list) result // $ExpectType number | undefined }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#findLast) ### findLastIndex ```typescript findLastIndex(predicate: (x: T) => boolean, list: T[]): number ``` It returns the index of the last element of `list` satisfying the `predicate` function. If there is no such element, then `-1` is returned. Try this R.findLastIndex example in Rambda REPL

All Typescript definitions

```typescript findLastIndex(predicate: (x: T) => boolean, list: T[]): number; findLastIndex(predicate: (x: T) => boolean): (list: T[]) => number; ```

R.findLastIndex source

```javascript export function findLastIndex(fn, list){ if (arguments.length === 1) return _list => findLastIndex(fn, _list) let index = list.length while (--index >= 0){ if (fn(list[ index ])){ return index } } return -1 } ```

Tests

```javascript import { findLastIndex } from './findLastIndex.js' test('happy', () => { const result = findLastIndex(x => x > 1, [ 1, 1, 1, 2, 3, 4, 1 ]) expect(result).toBe(5) expect(findLastIndex(x => x === 0, [ 0, 1, 1, 2, 3, 4, 1 ])).toBe(0) }) test('with curry', () => { expect(findLastIndex(x => x > 1)([ 1, 1, 1, 2, 3, 4, 1 ])).toBe(5) }) const obj1 = { x : 100 } const obj2 = { x : 200 } const a = [ 11, 10, 9, 'cow', obj1, 8, 7, 100, 200, 300, obj2, 4, 3, 2, 1, 0 ] const even = function (x){ return x % 2 === 0 } const gt100 = function (x){ return x > 100 } const isStr = function (x){ return typeof x === 'string' } const xGt100 = function (o){ return o && o.x > 100 } test('ramda 1', () => { expect(findLastIndex(even, a)).toBe(15) expect(findLastIndex(gt100, a)).toBe(9) expect(findLastIndex(isStr, a)).toBe(3) expect(findLastIndex(xGt100, a)).toBe(10) }) test('ramda 2', () => { expect(findLastIndex(even, [ 'zing' ])).toEqual(-1) }) test('ramda 3', () => { expect(findLastIndex(even, [ 2, 3, 5 ])).toBe(0) }) test('ramda 4', () => { expect(findLastIndex(even, [])).toEqual(-1) }) ```

Typescript test

```typescript import {findLastIndex} from 'rambda' const list = [1, 2, 3] describe('R.findLastIndex', () => { it('happy', () => { const predicate = (x: number) => x > 2 const result = findLastIndex(predicate, list) result // $ExpectType number }) it('curried', () => { const predicate = (x: number) => x > 2 const result = findLastIndex(predicate)(list) result // $ExpectType number }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#findLastIndex) ### flatten ```typescript flatten(list: any[]): T[] ``` It deeply flattens an array. Try this R.flatten example in Rambda REPL

All Typescript definitions

```typescript flatten(list: any[]): T[]; ```

R.flatten source

```javascript import { isArray } from './_internals/isArray.js' export function flatten(list, input){ const willReturn = input === undefined ? [] : input for (let i = 0; i < list.length; i++){ if (isArray(list[ i ])){ flatten(list[ i ], willReturn) } else { willReturn.push(list[ i ]) } } return willReturn } ```

Tests

```javascript import { flatten } from './flatten.js' test('happy', () => { expect(flatten([ 1, 2, 3, [ [ [ [ [ 4 ] ] ] ] ] ])).toEqual([ 1, 2, 3, 4 ]) expect(flatten([ 1, [ 2, [ [ 3 ] ] ], [ 4 ] ])).toEqual([ 1, 2, 3, 4 ]) expect(flatten([ 1, [ 2, [ [ [ 3 ] ] ] ], [ 4 ] ])).toEqual([ 1, 2, 3, 4 ]) expect(flatten([ 1, 2, [ 3, 4 ], 5, [ 6, [ 7, 8, [ 9, [ 10, 11 ], 12 ] ] ] ])).toEqual([ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 ]) }) test('readme example', () => { const result = flatten([ 1, 2, [ 3, 30, [ 300 ] ], [ 4 ] ]) expect(result).toEqual([ 1, 2, 3, 30, 300, 4 ]) }) ```

Typescript test

```typescript import {flatten} from 'rambda' describe('flatten', () => { it('happy', () => { const result = flatten([1, 2, [3, [4]]]) result // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#flatten) ### flip It returns function which calls `fn` with exchanged first and second argument. Try this R.flip example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#flip) ### forEach ```typescript forEach(fn: Iterator, list: T[]): T[] ``` It applies `iterable` function over all members of `list` and returns `list`. Try this R.forEach example in Rambda REPL

All Typescript definitions

```typescript forEach(fn: Iterator, list: T[]): T[]; forEach(fn: Iterator): (list: T[]) => T[]; forEach(fn: ObjectIterator, list: Dictionary): Dictionary; forEach(fn: ObjectIterator): (list: Dictionary) => Dictionary; ```

R.forEach source

```javascript import { isArray } from './_internals/isArray.js' import { keys } from './_internals/keys.js' export function forEach(fn, list){ if (arguments.length === 1) return _list => forEach(fn, _list) if (list === undefined){ return } if (isArray(list)){ let index = 0 const len = list.length while (index < len){ fn(list[ index ]) index++ } } else { let index = 0 const listKeys = keys(list) const len = listKeys.length while (index < len){ const key = listKeys[ index ] fn( list[ key ], key, list ) index++ } } return list } ```

Tests

```javascript import { forEach } from './forEach.js' import { type } from './type.js' test('happy', () => { const sideEffect = {} forEach(x => sideEffect[ `foo${ x }` ] = x + 10)([ 1, 2 ]) expect(sideEffect).toEqual({ foo1 : 11, foo2 : 12, }) }) test('iterate over object', () => { const obj = { a : 1, b : [ 1, 2 ], c : { d : 7 }, f : 'foo', } const result = {} const returned = forEach(( val, prop, inputObj ) => { expect(type(inputObj)).toBe('Object') result[ prop ] = `${ prop }-${ type(val) }` })(obj) const expected = { a : 'a-Number', b : 'b-Array', c : 'c-Object', f : 'f-String', } expect(result).toEqual(expected) expect(returned).toEqual(obj) }) test('with empty list', () => { const list = [] const result = forEach(x => x * x)(list) expect(result).toEqual(list) }) test('with wrong input', () => { const list = undefined const result = forEach(x => x * x)(list) expect(result).toBeUndefined() }) test('returns the input', () => { const list = [ 1, 2, 3 ] const result = forEach(x => x * x)(list) expect(result).toEqual(list) }) ```

Typescript test

```typescript import {forEach} from 'rambda' const list = [1, 2, 3] const obj = {a: 1, b: 2} describe('R.forEach with arrays', () => { it('happy', () => { const result = forEach(a => { a // $ExpectType number }, list) result // $ExpectType number[] }) it('curried require an explicit typing', () => { const result = forEach(a => { a // $ExpectType number })(list) result // $ExpectType number[] }) }) describe('R.forEach with objects', () => { it('happy', () => { const result = forEach((a, b, c) => { a // $ExpectType number b // $ExpectType string c // $ExpectType Dictionary return `${a}` }, obj) result // $ExpectType Dictionary }) it('curried require an input typing and a dummy third typing', () => { // Required in order all typings to work const result = forEach((a, b, c) => { a // $ExpectType number b // $ExpectType string c // $ExpectType Dictionary })(obj) result // $ExpectType Dictionary }) it('iterator without property', () => { const result = forEach(a => { a // $ExpectType number }, obj) result // $ExpectType Dictionary }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#forEach) ### fromPairs It transforms a `listOfPairs` to an object. Try this R.fromPairs example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#fromPairs) ### groupBy It splits `list` according to a provided `groupFn` function and returns an object. Try this R.groupBy example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#groupBy) ### groupWith It returns separated version of list or string `input`, where separation is done with equality `compareFn` function. Try this R.groupWith example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#groupWith) ### has ```typescript has(prop: string, obj: T): boolean ``` It returns `true` if `obj` has property `prop`. Try this R.has example in Rambda REPL

All Typescript definitions

```typescript has(prop: string, obj: T): boolean; has(prop: string): (obj: T) => boolean; ```

R.has source

```javascript export function has(prop, obj){ if (arguments.length === 1) return _obj => has(prop, _obj) if (!obj) return false return obj.hasOwnProperty(prop) } ```

Tests

```javascript import { has } from './has.js' test('happy', () => { expect(has('a')({ a : 1 })).toBeTrue() expect(has('b', { a : 1 })).toBeFalse() }) test('with non-object', () => { expect(has('a', undefined)).toBeFalse() expect(has('a', null)).toBeFalse() expect(has('a', true)).toBeFalse() expect(has('a', '')).toBeFalse() expect(has('a', /a/)).toBeFalse() }) ```

Typescript test

```typescript import {has} from 'rambda' describe('R.has', () => { it('happy', () => { const result = has('foo', {a: 1}) const curriedResult = has('bar')({a: 1}) result // $ExpectType boolean curriedResult // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#has) ### hasPath ```typescript hasPath( path: string | string[], input: object ): boolean ``` It will return true, if `input` object has truthy `path`(calculated with `R.path`). Try this R.hasPath example in Rambda REPL

All Typescript definitions

```typescript hasPath( path: string | string[], input: object ): boolean; hasPath( path: string | string[] ): (input: object) => boolean; ```

R.hasPath source

```javascript import { path } from './path.js' export function hasPath(pathInput, obj){ if (arguments.length === 1){ return objHolder => hasPath(pathInput, objHolder) } return path(pathInput, obj) !== undefined } ```

Tests

```javascript import { hasPath } from './hasPath.js' test('when true', () => { const path = 'a.b' const obj = { a : { b : [] } } const result = hasPath(path)(obj) const expectedResult = true expect(result).toEqual(expectedResult) }) test('when false', () => { const path = 'a.b' const obj = {} const result = hasPath(path, obj) const expectedResult = false expect(result).toEqual(expectedResult) }) ```

Typescript test

```typescript import {hasPath} from 'rambda' describe('R.hasPath', () => { it('string path', () => { const obj = {a: {b: 1}} const result = hasPath('a.b', obj) const curriedResult = hasPath('a.c')(obj) result // $ExpectType boolean curriedResult // $ExpectType boolean }) it('array path', () => { const obj = {a: {b: 1}} const result = hasPath(['a', 'b'], obj) const curriedResult = hasPath(['a', 'c'])(obj) result // $ExpectType boolean curriedResult // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#hasPath) ### head ```typescript head(input: string): string ``` It returns the first element of list or string `input`. Try this R.head example in Rambda REPL

All Typescript definitions

```typescript head(input: string): string; head(emptyList: []): undefined; head(input: T[]): T | undefined; ```

R.head source

```javascript export function head(listOrString){ if (typeof listOrString === 'string') return listOrString[ 0 ] || '' return listOrString[ 0 ] } ```

Tests

```javascript import { head } from './head.js' test('head', () => { expect(head([ 'fi', 'fo', 'fum' ])).toBe('fi') expect(head([])).toBeUndefined() expect(head('foo')).toBe('f') expect(head('')).toBe('') }) ```

Typescript test

```typescript import {head} from 'rambda' describe('R.head', () => { it('string', () => { const result = head('foo') result // $ExpectType string }) it('array', () => { const result = head([1, 2, 3]) result // $ExpectType number | undefined }) it('empty array - case 1', () => { const result = head([]) result // $ExpectType undefined }) it('empty array - case 2', () => { const list = ['foo', 'bar'].filter(x => x.startsWith('a')) const result = head(list) result // $ExpectType string | undefined }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#head) ### identical It returns `true` if its arguments `a` and `b` are identical. Otherwise, it returns `false`. Try this R.identical example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#identical) ### identity ```typescript identity(input: T): T ``` It just passes back the supplied `input` argument. Try this R.identity example in Rambda REPL

All Typescript definitions

```typescript identity(input: T): T; ```

R.identity source

```javascript export function identity(x){ return x } ```

Tests

```javascript import { identity } from './identity.js' test('happy', () => { expect(identity(7)).toBe(7) expect(identity(true)).toBeTrue() expect(identity({ a : 1 })).toEqual({ a : 1 }) }) ```

Typescript test

```typescript import {identity} from 'rambda' describe('R.identity', () => { it('happy', () => { const result = identity(4) result // $ExpectType 4 }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#identity) ### ifElse ```typescript ifElse( pred: (a: T) => a is TFiltered, onTrue: (a: TFiltered) => TOnTrueResult, onFalse: (a: Exclude) => TOnFalseResult, ): (a: T) => TOnTrueResult | TOnFalseResult ``` It expects `condition`, `onTrue` and `onFalse` functions as inputs and it returns a new function with example name of `fn`. When `fn`` is called with `input` argument, it will return either `onTrue(input)` or `onFalse(input)` depending on `condition(input)` evaluation. Try this R.ifElse example in Rambda REPL

All Typescript definitions

```typescript ifElse( pred: (a: T) => a is TFiltered, onTrue: (a: TFiltered) => TOnTrueResult, onFalse: (a: Exclude) => TOnFalseResult, ): (a: T) => TOnTrueResult | TOnFalseResult; ifElse(fn: (...args: TArgs) => boolean, onTrue: (...args: TArgs) => TOnTrueResult, onFalse: (...args: TArgs) => TOnFalseResult): (...args: TArgs) => TOnTrueResult | TOnFalseResult; ```

R.ifElse source

```javascript import { curry } from './curry.js' function ifElseFn( condition, onTrue, onFalse ){ return (...input) => { const conditionResult = typeof condition === 'boolean' ? condition : condition(...input) if (conditionResult === true){ return onTrue(...input) } return onFalse(...input) } } export const ifElse = curry(ifElseFn) ```

Tests

```javascript import { always } from './always.js' import { has } from './has.js' import { identity } from './identity.js' import { ifElse } from './ifElse.js' import { prop } from './prop.js' const condition = has('foo') const v = function (a){ return typeof a === 'number' } const t = function (a){ return a + 1 } const ifFn = x => prop('foo', x).length const elseFn = () => false test('happy', () => { const fn = ifElse(condition, ifFn)(elseFn) expect(fn({ foo : 'bar' })).toBe(3) expect(fn({ fo : 'bar' })).toBeFalse() }) test('ramda spec', () => { const ifIsNumber = ifElse(v) expect(ifIsNumber(t, identity)(15)).toBe(16) expect(ifIsNumber(t, identity)('hello')).toBe('hello') }) test('pass all arguments', () => { const identity = function (a){ return a } const v = function (){ return true } const onTrue = function (a, b){ expect(a).toBe(123) expect(b).toBe('abc') } ifElse( v, onTrue, identity )(123, 'abc') }) test('accept constant as condition', () => { const fn = ifElse(true)(always(true))(always(false)) expect(fn()).toBeTrue() }) test('accept constant as condition - case 2', () => { const fn = ifElse( false, always(true), always(false) ) expect(fn()).toBeFalse() }) test('curry 1', () => { const fn = ifElse(condition, ifFn)(elseFn) expect(fn({ foo : 'bar' })).toBe(3) expect(fn({ fo : 'bar' })).toBeFalse() }) test('curry 2', () => { const fn = ifElse(condition)(ifFn)(elseFn) expect(fn({ foo : 'bar' })).toBe(3) expect(fn({ fo : 'bar' })).toBeFalse() }) test('simple arity of 1', () => { const condition = x => x > 5 const onTrue = x => x + 1 const onFalse = x => x + 10 const result = ifElse( condition, onTrue, onFalse )(1) expect(result).toBe(11) }) test('simple arity of 2', () => { const condition = (x, y) => x + y > 5 const onTrue = (x, y) => x + y + 1 const onFalse = (x, y) => x + y + 10 const result = ifElse( condition, onTrue, onFalse )(1, 10) expect(result).toBe(12) }) ```

Typescript test

```typescript import {ifElse} from 'rambda' describe('R.ifElse', () => { it('happy', () => { const condition = (x: number) => x > 5 const onTrue = (x: number) => `foo${x}` const onFalse = (x: number) => `bar${x}` const fn = ifElse(condition, onTrue, onFalse) fn // $ExpectType (x: number) => string const result = fn(3) result // $ExpectType string }) it('arity of 2', () => { const condition = (x: number, y: string) => x + y.length > 5 const onTrue = (x: number, y: string) => `foo${x}-${y}` const onFalse = (x: number, y: string) => `bar${x}-${y}` const fn = ifElse(condition, onTrue, onFalse) fn // $ExpectType (x: number, y: string) => string const result = fn(3, 'hello') result // $ExpectType string }) test('DefinitelyTyped#59291', () => { const getLengthIfStringElseDouble = ifElse( (a: string | number): a is string => true, a => a.length, a => a * 2 ) getLengthIfStringElseDouble('foo') // $ExpectType number getLengthIfStringElseDouble(3) // $ExpectType number const result = ifElse( (a: { foo?: string, bar: number | string, }): a is {foo: string, bar: string} => true, (a): [string, string] => [a.foo, a.bar], (a): [string | undefined, string | number] => [a.foo, a.bar] ) result // $ExpectType (a: { foo?: string | undefined; bar: string | number; }) => [string, string] | [string | undefined, string | number] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#ifElse) ### inc It increments a number. Try this R.inc example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#inc) ### includes ```typescript includes(valueToFind: string, input: string[] | string): boolean ``` If `input` is string, then this method work as native `String.includes`. If `input` is array, then `R.equals` is used to define if `valueToFind` belongs to the list. Try this R.includes example in Rambda REPL

All Typescript definitions

```typescript includes(valueToFind: string, input: string[] | string): boolean; includes(valueToFind: string): (input: string[] | string) => boolean; includes(valueToFind: T, input: T[]): boolean; includes(valueToFind: T): (input: T[]) => boolean; ```

R.includes source

```javascript import { isArray } from './_internals/isArray.js' import { _indexOf } from './equals.js' export function includes(valueToFind, iterable){ if (arguments.length === 1) return _iterable => includes(valueToFind, _iterable) if (typeof iterable === 'string'){ return iterable.includes(valueToFind) } if (!iterable){ throw new TypeError(`Cannot read property \'indexOf\' of ${ iterable }`) } if (!isArray(iterable)) return false return _indexOf(valueToFind, iterable) > -1 } ```

Tests

```javascript import { includes as includesRamda } from 'ramda' import { includes } from './includes.js' test('with string as iterable', () => { const str = 'foo bar' expect(includes('bar')(str)).toBeTrue() expect(includesRamda('bar')(str)).toBeTrue() expect(includes('never', str)).toBeFalse() expect(includesRamda('never', str)).toBeFalse() }) test('with array as iterable', () => { const arr = [ 1, 2, 3 ] expect(includes(2)(arr)).toBeTrue() expect(includesRamda(2)(arr)).toBeTrue() expect(includes(4, arr)).toBeFalse() expect(includesRamda(4, arr)).toBeFalse() }) test('with list of objects as iterable', () => { const arr = [ { a : 1 }, { b : 2 }, { c : 3 } ] expect(includes({ c : 3 }, arr)).toBeTrue() expect(includesRamda({ c : 3 }, arr)).toBeTrue() }) test('with NaN', () => { const result = includes(NaN, [ NaN ]) const ramdaResult = includesRamda(NaN, [ NaN ]) expect(result).toBeTrue() expect(ramdaResult).toBeTrue() }) test('with wrong input that does not throw', () => { const result = includes(1, /foo/g) const ramdaResult = includesRamda(1, /foo/g) expect(result).toBeFalse() expect(ramdaResult).toBeFalse() }) test('throws on wrong input - match ramda behaviour', () => { expect(() => includes(2, null)).toThrowWithMessage(TypeError, 'Cannot read property \'indexOf\' of null') expect(() => includesRamda(2, null)).toThrowWithMessage(TypeError, 'Cannot read properties of null (reading \'indexOf\')') expect(() => includes(2, undefined)).toThrowWithMessage(TypeError, 'Cannot read property \'indexOf\' of undefined') expect(() => includesRamda(2, undefined)).toThrowWithMessage(TypeError, 'Cannot read properties of undefined (reading \'indexOf\')') }) ```

Typescript test

```typescript import {includes} from 'rambda' const list = [{a: {b: '1'}}, {a: {c: '2'}}, {a: {b: '3'}}] describe('R.includes', () => { it('happy', () => { const result = includes({a: {b: '1'}}, list) result // $ExpectType boolean }) it('with string', () => { const result = includes('oo', 'foo') const curriedResult = includes('oo')('foo') result // $ExpectType boolean curriedResult // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#includes) ### indexBy It generates object with properties provided by `condition` and values provided by `list` array. If `condition` is a function, then all list members are passed through it. If `condition` is a string, then all list members are passed through `R.path(condition)`. Try this R.indexBy example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#indexBy) ### indexOf It returns the index of the first element of `list` equals to `valueToFind`. If there is no such element, it returns `-1`. Try this R.indexOf example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#indexOf) ### init ```typescript init(input: T): T extends readonly [...infer U, any] ? U : [...T] ``` It returns all but the last element of list or string `input`. Try this R.init example in Rambda REPL

All Typescript definitions

```typescript init(input: T): T extends readonly [...infer U, any] ? U : [...T]; init(input: string): string; ```

R.init source

```javascript import baseSlice from './_internals/baseSlice.js' export function init(listOrString){ if (typeof listOrString === 'string') return listOrString.slice(0, -1) return listOrString.length ? baseSlice( listOrString, 0, -1 ) : [] } ```

Tests

```javascript import { init } from './init.js' test('with array', () => { expect(init([ 1, 2, 3 ])).toEqual([ 1, 2 ]) expect(init([ 1, 2 ])).toEqual([ 1 ]) expect(init([ 1 ])).toEqual([]) expect(init([])).toEqual([]) expect(init([])).toEqual([]) expect(init([ 1 ])).toEqual([]) }) test('with string', () => { expect(init('foo')).toBe('fo') expect(init('f')).toBe('') expect(init('')).toBe('') }) ```

Typescript test

```typescript import {init} from 'rambda' describe('R.init', () => { it('with string', () => { const result = init('foo') result // $ExpectType string }) it('with list - one type', () => { const result = init([1, 2, 3]) result // $ExpectType number[] }) it('with list - mixed types', () => { const result = init([1, 2, 3, 'foo', 'bar']) result // $ExpectType (string | number)[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#init) ### intersection It loops through `listA` and `listB` and returns the intersection of the two according to `R.equals`. Try this R.intersection example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#intersection) ### intersperse It adds a `separator` between members of `list`. Try this R.intersperse example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#intersperse) ### is It returns `true` if `x` is instance of `targetPrototype`. Try this R.is example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#is) ### isEmpty ```typescript isEmpty(x: T): boolean ``` It returns `true` if `x` is `empty`. Try this R.isEmpty example in Rambda REPL

All Typescript definitions

```typescript isEmpty(x: T): boolean; ```

R.isEmpty source

```javascript import { type } from './type.js' export function isEmpty(input){ const inputType = type(input) if ([ 'Undefined', 'NaN', 'Number', 'Null' ].includes(inputType)) return false if (!input) return true if (inputType === 'Object'){ return Object.keys(input).length === 0 } if (inputType === 'Array'){ return input.length === 0 } return false } ```

Tests

```javascript import { isEmpty } from './isEmpty.js' test('happy', () => { expect(isEmpty(undefined)).toBeFalse() expect(isEmpty('')).toBeTrue() expect(isEmpty(null)).toBeFalse() expect(isEmpty(' ')).toBeFalse() expect(isEmpty(new RegExp(''))).toBeFalse() expect(isEmpty([])).toBeTrue() expect(isEmpty([ [] ])).toBeFalse() expect(isEmpty({})).toBeTrue() expect(isEmpty({ x : 0 })).toBeFalse() expect(isEmpty(0)).toBeFalse() expect(isEmpty(NaN)).toBeFalse() expect(isEmpty([ '' ])).toBeFalse() }) ```

Typescript test

```typescript import {isEmpty} from 'rambda' describe('R.isEmpty', () => { it('happy', () => { const result = isEmpty('foo') result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#isEmpty) ### isNil ```typescript isNil(x: any): x is null | undefined ``` It returns `true` if `x` is either `null` or `undefined`. Try this R.isNil example in Rambda REPL

All Typescript definitions

```typescript isNil(x: any): x is null | undefined; ```

R.isNil source

```javascript export function isNil(x){ return x === undefined || x === null } ```

Tests

```javascript import { isNil } from './isNil.js' test('happy', () => { expect(isNil(null)).toBeTrue() expect(isNil(undefined)).toBeTrue() expect(isNil([])).toBeFalse() }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#isNil) ### join ```typescript join(glue: string, list: T[]): string ``` It returns a string of all `list` instances joined with a `glue`. Try this R.join example in Rambda REPL

All Typescript definitions

```typescript join(glue: string, list: T[]): string; join(glue: string): (list: T[]) => string; ```

R.join source

```javascript export function join(glue, list){ if (arguments.length === 1) return _list => join(glue, _list) return list.join(glue) } ```

Tests

```javascript import { join } from './join.js' test('curry', () => { expect(join('|')([ 'foo', 'bar', 'baz' ])).toBe('foo|bar|baz') expect(join('|', [ 1, 2, 3 ])).toBe('1|2|3') const spacer = join(' ') expect(spacer([ 'a', 2, 3.4 ])).toBe('a 2 3.4') }) ```

Typescript test

```typescript import {join} from 'rambda' describe('R.join', () => { it('happy', () => { const result = join('|', [1, 2, 3]) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#join) ### juxt ```typescript juxt(fns: [(...a: A) => R1]): (...a: A) => [R1] ``` It applies list of function to a list of inputs. Try this R.juxt example in Rambda REPL

All Typescript definitions

```typescript juxt(fns: [(...a: A) => R1]): (...a: A) => [R1]; juxt (fns: [(...a: A) => R1, (...a: A) => R2]): (...a: A) => [R1, R2]; juxt (fns: [(...a: A) => R1, (...a: A) => R2, (...a: A) => R3]): (...a: A) => [R1, R2, R3]; juxt (fns: [(...a: A) => R1, (...a: A) => R2, (...a: A) => R3, (...a: A) => R4]): (...a: A) => [R1, R2, R3, R4]; juxt (fns: [(...a: A) => R1, (...a: A) => R2, (...a: A) => R3, (...a: A) => R4, (...a: A) => R5]): (...a: A) => [R1, R2, R3, R4, R5]; juxt (fns: Array<(...args: A) => U>): (...args: A) => U[]; ```

R.juxt source

```javascript export function juxt(listOfFunctions){ return (...args) => listOfFunctions.map(fn => fn(...args)) } ```

Tests

```javascript import { juxt } from './juxt.js' test('happy', () => { const fn = juxt([ Math.min, Math.max, Math.min ]) const result = fn( 3, 4, 9, -3 ) expect(result).toEqual([ -3, 9, -3 ]) }) ```

Typescript test

```typescript import {juxt} from 'rambda' describe('R.juxt', () => { it('happy', () => { const fn = juxt([Math.min, Math.max]) const result = fn(3, 4, 9, -3) result // $ExpectType [number, number] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#juxt) ### keys ```typescript keys(x: T): (keyof T)[] ``` It applies `Object.keys` over `x` and returns its keys. Try this R.keys example in Rambda REPL

All Typescript definitions

```typescript keys(x: T): (keyof T)[]; keys(x: T): string[]; ```

R.keys source

```javascript export function keys(x){ return Object.keys(x) } ```

Tests

```javascript import { keys } from './keys.js' test('happy', () => { expect(keys({ a : 1 })).toEqual([ 'a' ]) }) ```

Typescript test

```typescript import {keys} from 'rambda' const obj = {a: 1, b: 2} describe('R.keys', () => { it('happy', () => { const result = keys(obj) result // $ExpectType ("b" | "a")[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#keys) ### last ```typescript last(str: string): string ``` It returns the last element of `input`, as the `input` can be either a string or an array. Try this R.last example in Rambda REPL

All Typescript definitions

```typescript last(str: string): string; last(emptyList: []): undefined; last(list: T[]): T | undefined; ```

R.last source

```javascript export function last(listOrString){ if (typeof listOrString === 'string'){ return listOrString[ listOrString.length - 1 ] || '' } return listOrString[ listOrString.length - 1 ] } ```

Tests

```javascript import { last } from './last.js' test('with list', () => { expect(last([ 1, 2, 3 ])).toBe(3) expect(last([])).toBeUndefined() }) test('with string', () => { expect(last('abc')).toBe('c') expect(last('')).toBe('') }) ```

Typescript test

```typescript import {last} from 'rambda' describe('R.last', () => { it('string', () => { const result = last('foo') result // $ExpectType string }) it('array', () => { const result = last([1, 2, 3]) result // $ExpectType number | undefined }) it('empty array - case 1', () => { const result = last([]) result // $ExpectType undefined }) it('empty array - case 2', () => { const list = ['foo', 'bar'].filter(x => x.startsWith('a')) const result = last(list) result // $ExpectType string | undefined }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#last) ### lastIndexOf ```typescript lastIndexOf(target: T, list: T[]): number ``` It returns the last index of `target` in `list` array. `R.equals` is used to determine equality between `target` and members of `list`. If there is no such index, then `-1` is returned. Try this R.lastIndexOf example in Rambda REPL

All Typescript definitions

```typescript lastIndexOf(target: T, list: T[]): number; lastIndexOf(target: T): (list: T[]) => number; ```

R.lastIndexOf source

```javascript import { _lastIndexOf } from './equals.js' export function lastIndexOf(valueToFind, list){ if (arguments.length === 1){ return _list => _lastIndexOf(valueToFind, _list) } return _lastIndexOf(valueToFind, list) } ```

Tests

```javascript import { lastIndexOf as lastIndexOfRamda } from 'ramda' import { compareCombinations } from './_internals/testUtils.js' import { possibleIterables, possibleTargets } from './indexOf.spec.js' import { lastIndexOf } from './lastIndexOf.js' test('with NaN', () => { expect(lastIndexOf(NaN, [ NaN ])).toBe(0) }) test('will throw with bad input', () => { expect(lastIndexOfRamda([], true)).toEqual(-1) expect(() => indexOf([], true)).toThrowErrorMatchingInlineSnapshot('"indexOf is not defined"') }) test('without list of objects - no R.equals', () => { expect(lastIndexOf(3, [ 1, 2, 3, 4 ])).toBe(2) expect(lastIndexOf(10)([ 1, 2, 3, 4 ])).toEqual(-1) }) test('list of objects uses R.equals', () => { const listOfObjects = [ { a : 1 }, { b : 2 }, { c : 3 } ] expect(lastIndexOf({ c : 4 }, listOfObjects)).toBe(-1) expect(lastIndexOf({ c : 3 }, listOfObjects)).toBe(2) }) test('list of arrays uses R.equals', () => { const listOfLists = [ [ 1 ], [ 2, 3 ], [ 2, 3, 4 ], [ 2, 3 ], [ 1 ], [] ] expect(lastIndexOf([], listOfLists)).toBe(5) expect(lastIndexOf([ 1 ], listOfLists)).toBe(4) expect(lastIndexOf([ 2, 3, 4 ], listOfLists)).toBe(2) expect(lastIndexOf([ 2, 3, 5 ], listOfLists)).toBe(-1) }) test('with string as iterable', () => { expect(() => lastIndexOf('a', 'abc')).toThrowErrorMatchingInlineSnapshot('"Cannot read property \'indexOf\' of abc"') expect(lastIndexOfRamda('a', 'abc')).toBe(0) }) describe('brute force', () => { compareCombinations({ fn : lastIndexOf, fnRamda : lastIndexOfRamda, firstInput : possibleTargets, secondInput : possibleIterables, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 34, "RESULTS_MISMATCH": 0, "SHOULD_NOT_THROW": 51, "SHOULD_THROW": 0, "TOTAL_TESTS": 170, } `) }, }) }) ```

Typescript test

```typescript import {lastIndexOf} from 'rambda' const list = [1, 2, 3] describe('R.lastIndexOf', () => { it('happy', () => { const result = lastIndexOf(2, list) result // $ExpectType number }) it('curried', () => { const result = lastIndexOf(2)(list) result // $ExpectType number }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#lastIndexOf) ### length ```typescript length(input: T[]): number ``` It returns the `length` property of list or string `input`. Try this R.length example in Rambda REPL

All Typescript definitions

```typescript length(input: T[]): number; ```

R.length source

```javascript import { isArray } from './_internals/isArray.js' export function length(x){ if (isArray(x)) return x.length if (typeof x === 'string') return x.length return NaN } ```

Tests

```javascript import { length as lengthRamda } from 'ramda' import { length } from './length.js' test('happy', () => { expect(length('foo')).toBe(3) expect(length([ 1, 2, 3 ])).toBe(3) expect(length([])).toBe(0) }) test('with empty string', () => { expect(length('')).toBe(0) }) test('with bad input returns NaN', () => { expect(length(0)).toBeNaN() expect(length({})).toBeNaN() expect(length(null)).toBeNaN() expect(length(undefined)).toBeNaN() }) test('with length as property', () => { const input1 = { length : '123' } const input2 = { length : null } const input3 = { length : '' } expect(length(input1)).toBeNaN() expect(lengthRamda(input1)).toBeNaN() expect(length(input2)).toBeNaN() expect(lengthRamda(input2)).toBeNaN() expect(length(input3)).toBeNaN() expect(lengthRamda(input3)).toBeNaN() }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#length) ### lens ```typescript lens(getter: (s: T) => U, setter: (a: U, s: T) => V): Lens ``` It returns a `lens` for the given `getter` and `setter` functions. The `getter` **gets** the value of the focus; the `setter` **sets** the value of the focus. The setter should not mutate the data structure. Try this R.lens example in Rambda REPL

All Typescript definitions

```typescript lens(getter: (s: T) => U, setter: (a: U, s: T) => V): Lens; ```

R.lens source

```javascript export function lens(getter, setter){ return function (functor){ return function (target){ return functor(getter(target)).map(focus => setter(focus, target)) } } } ```

Typescript test

```typescript import {lens, assoc} from 'rambda' interface Input { foo: string, } describe('R.lens', () => { it('happy', () => { const fn = lens((x: Input) => { x.foo // $ExpectType string return x.foo }, assoc('name')) fn // $ExpectType Lens }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#lens) ### lensIndex ```typescript lensIndex(index: number): Lens ``` It returns a lens that focuses on specified `index`. Try this R.lensIndex example in Rambda REPL

All Typescript definitions

```typescript lensIndex(index: number): Lens; ```

R.lensIndex source

```javascript import { lens } from './lens.js' import { nth } from './nth.js' import { update } from './update.js' export function lensIndex(index){ return lens(nth(index), update(index)) } ```

Tests

```javascript import { compose } from './compose.js' import { keys } from './keys.js' import { lensIndex } from './lensIndex.js' import { over } from './over.js' import { set } from './set.js' import { view } from './view.js' const testList = [ { a : 1 }, { b : 2 }, { c : 3 } ] test('focuses list element at the specified index', () => { expect(view(lensIndex(0), testList)).toEqual({ a : 1 }) }) test('returns undefined if the specified index does not exist', () => { expect(view(lensIndex(10), testList)).toBeUndefined() }) test('sets the list value at the specified index', () => { expect(set( lensIndex(0), 0, testList )).toEqual([ 0, { b : 2 }, { c : 3 } ]) }) test('applies function to the value at the specified list index', () => { expect(over( lensIndex(2), keys, testList )).toEqual([ { a : 1 }, { b : 2 }, [ 'c' ] ]) }) test('can be composed', () => { const nestedList = [ 0, [ 10, 11, 12 ], 1, 2 ] const composedLens = compose(lensIndex(1), lensIndex(0)) expect(view(composedLens, nestedList)).toBe(10) }) test('set s (get s) === s', () => { expect(set( lensIndex(0), view(lensIndex(0), testList), testList )).toEqual(testList) }) test('get (set s v) === v', () => { expect(view(lensIndex(0), set( lensIndex(0), 0, testList ))).toBe(0) }) test('get (set(set s v1) v2) === v2', () => { expect(view(lensIndex(0), set( lensIndex(0), 11, set( lensIndex(0), 10, testList ) ))).toBe(11) }) ```

Typescript test

```typescript import {view, lensIndex} from 'rambda' interface Input { a: number, } const testList: Input[] = [{a: 1}, {a: 2}, {a: 3}] describe('R.lensIndex', () => { it('happy', () => { const result = view(lensIndex(0), testList) result // $ExpectType Input result.a // $ExpectType number }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#lensIndex) ### lensPath ```typescript lensPath(path: RamdaPath): Lens ``` It returns a lens that focuses on specified `path`. Try this R.lensPath example in Rambda REPL

All Typescript definitions

```typescript lensPath(path: RamdaPath): Lens; lensPath(path: string): Lens; ```

R.lensPath source

```javascript import { assocPath } from './assocPath.js' import { lens } from './lens.js' import { path } from './path.js' export function lensPath(key){ return lens(path(key), assocPath(key)) } ```

Tests

```javascript import { compose } from './compose.js' import { identity } from './identity.js' import { inc } from './inc.js' import { lensPath } from './lensPath.js' import { lensProp } from './lensProp.js' import { over } from './over.js' import { set } from './set.js' import { view } from './view.js' const testObj = { a : [ { b : 1 }, { b : 2 } ], d : 3, } test('view', () => { expect(view(lensPath('d'), testObj)).toBe(3) expect(view(lensPath('a.0.b'), testObj)).toBe(1) // this is different to ramda, as ramda will return a clone of the input object expect(view(lensPath(''), testObj)).toBeUndefined() }) test('set', () => { expect(set( lensProp('d'), 0, testObj )).toEqual({ a : [ { b : 1 }, { b : 2 } ], d : 0, }) expect(set( lensPath('a.0.b'), 0, testObj )).toEqual({ a : [ { b : 0 }, { b : 2 } ], d : 3, }) expect(set( lensPath('a.0.X'), 0, testObj )).toEqual({ a : [ { b : 1, X : 0, }, { b : 2 }, ], d : 3, }) expect(set( lensPath([]), 0, testObj )).toBe(0) }) test('over', () => { expect(over( lensPath('d'), inc, testObj )).toEqual({ a : [ { b : 1 }, { b : 2 } ], d : 4, }) expect(over( lensPath('a.1.b'), inc, testObj )).toEqual({ a : [ { b : 1 }, { b : 3 } ], d : 3, }) expect(over( lensProp('X'), identity, testObj )).toEqual({ a : [ { b : 1 }, { b : 2 } ], d : 3, X : undefined, }) expect(over( lensPath('a.0.X'), identity, testObj )).toEqual({ a : [ { b : 1, X : undefined, }, { b : 2 }, ], d : 3, }) }) test('compose', () => { const composedLens = compose(lensPath('a'), lensPath('1.b')) expect(view(composedLens, testObj)).toBe(2) }) test('set s (get s) === s', () => { expect(set( lensPath([ 'd' ]), view(lensPath([ 'd' ]), testObj), testObj )).toEqual(testObj) expect(set( lensPath([ 'a', 0, 'b' ]), view(lensPath([ 'a', 0, 'b' ]), testObj), testObj )).toEqual(testObj) }) test('get (set s v) === v', () => { expect(view(lensPath([ 'd' ]), set( lensPath([ 'd' ]), 0, testObj ))).toBe(0) expect(view(lensPath([ 'a', 0, 'b' ]), set( lensPath([ 'a', 0, 'b' ]), 0, testObj ))).toBe(0) }) test('get (set(set s v1) v2) === v2', () => { const p = [ 'd' ] const q = [ 'a', 0, 'b' ] expect(view(lensPath(p), set( lensPath(p), 11, set( lensPath(p), 10, testObj ) ))).toBe(11) expect(view(lensPath(q), set( lensPath(q), 11, set( lensPath(q), 10, testObj ) ))).toBe(11) }) ```

Typescript test

```typescript import {lensPath, view} from 'rambda' interface Input { foo: number[], bar: { a: string, b: string, }, } const testObject: Input = { foo: [1, 2], bar: { a: 'x', b: 'y', }, } const path = lensPath(['bar', 'a']) const pathAsString = lensPath('bar.a') describe('R.lensPath', () => { it('happy', () => { const result = view(path, testObject) result // $ExpectType string }) it('using string as path input', () => { const result = view(pathAsString, testObject) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#lensPath) ### lensProp ```typescript lensProp(prop: string): { (obj: T): U ``` It returns a lens that focuses on specified property `prop`. Try this R.lensProp example in Rambda REPL

All Typescript definitions

```typescript lensProp(prop: string): { (obj: T): U; set(val: T, obj: U): V; }; ```

R.lensProp source

```javascript import { assoc } from './assoc.js' import { lens } from './lens.js' import { prop } from './prop.js' export function lensProp(key){ return lens(prop(key), assoc(key)) } ```

Tests

```javascript import { compose } from './compose.js' import { identity } from './identity.js' import { inc } from './inc.js' import { lensProp } from './lensProp.js' import { over } from './over.js' import { set } from './set.js' import { view } from './view.js' const testObj = { a : 1, b : 2, c : 3, } test('focuses object the specified object property', () => { expect(view(lensProp('a'), testObj)).toBe(1) }) test('returns undefined if the specified property does not exist', () => { expect(view(lensProp('X'), testObj)).toBeUndefined() }) test('sets the value of the object property specified', () => { expect(set( lensProp('a'), 0, testObj )).toEqual({ a : 0, b : 2, c : 3, }) }) test('adds the property to the object if it doesn\'t exist', () => { expect(set( lensProp('d'), 4, testObj )).toEqual({ a : 1, b : 2, c : 3, d : 4, }) }) test('applies function to the value of the specified object property', () => { expect(over( lensProp('a'), inc, testObj )).toEqual({ a : 2, b : 2, c : 3, }) }) test('applies function to undefined and adds the property if it doesn\'t exist', () => { expect(over( lensProp('X'), identity, testObj )).toEqual({ a : 1, b : 2, c : 3, X : undefined, }) }) test('can be composed', () => { const nestedObj = { a : { b : 1 }, c : 2, } const composedLens = compose(lensProp('a'), lensProp('b')) expect(view(composedLens, nestedObj)).toBe(1) }) test('set s (get s) === s', () => { expect(set( lensProp('a'), view(lensProp('a'), testObj), testObj )).toEqual(testObj) }) test('get (set s v) === v', () => { expect(view(lensProp('a'), set( lensProp('a'), 0, testObj ))).toBe(0) }) test('get (set(set s v1) v2) === v2', () => { expect(view(lensProp('a'), set( lensProp('a'), 11, set( lensProp('a'), 10, testObj ) ))).toBe(11) }) ```

Typescript test

```typescript import {lensProp, view} from 'rambda' interface Input { foo: string, } const testObject: Input = { foo: 'Led Zeppelin', } const lens = lensProp('foo') describe('R.lensProp', () => { it('happy', () => { const result = view(lens, testObject) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#lensProp) ### map ```typescript map(fn: ObjectIterator, iterable: Dictionary): Dictionary ``` It returns the result of looping through `iterable` with `fn`. It works with both array and object. Try this R.map example in Rambda REPL

All Typescript definitions

```typescript map(fn: ObjectIterator, iterable: Dictionary): Dictionary; map(fn: Iterator, iterable: T[]): U[]; map(fn: Iterator): (iterable: T[]) => U[]; map(fn: ObjectIterator): (iterable: Dictionary) => Dictionary; map(fn: Iterator): (iterable: T[]) => T[]; map(fn: Iterator, iterable: T[]): T[]; ```

R.map source

```javascript import { INCORRECT_ITERABLE_INPUT } from './_internals/constants.js' import { isArray } from './_internals/isArray.js' import { keys } from './_internals/keys.js' export function mapArray( fn, list, isIndexed = false ){ let index = 0 const willReturn = Array(list.length) while (index < list.length){ willReturn[ index ] = isIndexed ? fn(list[ index ], index) : fn(list[ index ]) index++ } return willReturn } export function mapObject(fn, obj){ if (arguments.length === 1){ return _obj => mapObject(fn, _obj) } let index = 0 const objKeys = keys(obj) const len = objKeys.length const willReturn = {} while (index < len){ const key = objKeys[ index ] willReturn[ key ] = fn( obj[ key ], key, obj ) index++ } return willReturn } export const mapObjIndexed = mapObject export function map(fn, iterable){ if (arguments.length === 1) return _iterable => map(fn, _iterable) if (!iterable){ throw new Error(INCORRECT_ITERABLE_INPUT) } if (isArray(iterable)) return mapArray(fn, iterable) return mapObject(fn, iterable) } ```

Tests

```javascript import { map as mapRamda } from 'ramda' import { map } from './map.js' const double = x => x * 2 describe('with array', () => { it('happy', () => { expect(map(double, [ 1, 2, 3 ])).toEqual([ 2, 4, 6 ]) }) it('curried', () => { expect(map(double)([ 1, 2, 3 ])).toEqual([ 2, 4, 6 ]) }) }) describe('with object', () => { const obj = { a : 1, b : 2, } it('happy', () => { expect(map(double, obj)).toEqual({ a : 2, b : 4, }) }) it('property as second and input object as third argument', () => { const obj = { a : 1, b : 2, } const iterator = ( val, prop, inputObject ) => { expect(prop).toBeString() expect(inputObject).toEqual(obj) return val * 2 } expect(map(iterator)(obj)).toEqual({ a : 2, b : 4, }) }) }) test('bad inputs difference between Ramda and Rambda', () => { expect(() => map(double, null)).toThrowErrorMatchingInlineSnapshot('"Incorrect iterable input"') expect(() => map(double)(undefined)).toThrowErrorMatchingInlineSnapshot('"Incorrect iterable input"') expect(() => mapRamda(double, null)).toThrowErrorMatchingInlineSnapshot('"Cannot read properties of null (reading \'fantasy-land/map\')"') expect(() => mapRamda(double, undefined)).toThrowErrorMatchingInlineSnapshot('"Cannot read properties of undefined (reading \'fantasy-land/map\')"') }) ```

Typescript test

```typescript import {map} from 'rambda' describe('R.map with arrays', () => { it('iterable returns the same type as the input', () => { const result = map( (x: number) => { x // $ExpectType number return x + 2 }, [1, 2, 3] ) result // $ExpectType number[] }) it('iterable returns the same type as the input - curried', () => { const result = map((x: number) => { x // $ExpectType number return x + 2 })([1, 2, 3]) result // $ExpectType number[] }) it('iterable returns different type as the input', () => { const result = map( (x: number) => { x // $ExpectType number return String(x) }, [1, 2, 3] ) result // $ExpectType string[] }) }) describe('R.map with objects', () => { it('iterable with all three arguments - curried', () => { // It requires dummy third typing argument // in order to identify compared to curry typings for arrays // ============================================ const result = map((a, b, c) => { a // $ExpectType number b // $ExpectType string c // $ExpectType Dictionary return `${a}` })({a: 1, b: 2}) result // $ExpectType Dictionary }) it('iterable with all three arguments', () => { const result = map( (a, b, c) => { a // $ExpectType number b // $ExpectType string c // $ExpectType Dictionary return `${a}` }, {a: 1, b: 2} ) result // $ExpectType Dictionary }) it('iterable with property argument', () => { const result = map( (a, b) => { a // $ExpectType number b // $ExpectType string return `${a}` }, {a: 1, b: 2} ) result // $ExpectType Dictionary }) it('iterable with no property argument', () => { const result = map( a => { a // $ExpectType number return `${a}` }, {a: 1, b: 2} ) result // $ExpectType Dictionary }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#map) ### mapObjIndexed ```typescript mapObjIndexed(fn: ObjectIterator, iterable: Dictionary): Dictionary ``` It works the same way as `R.map` does for objects. It is added as Ramda also has this method. Try this R.mapObjIndexed example in Rambda REPL

All Typescript definitions

```typescript mapObjIndexed(fn: ObjectIterator, iterable: Dictionary): Dictionary; mapObjIndexed(fn: ObjectIterator, iterable: Dictionary): Dictionary; mapObjIndexed(fn: ObjectIterator): (iterable: Dictionary) => Dictionary; mapObjIndexed(fn: ObjectIterator): (iterable: Dictionary) => Dictionary; ```

Typescript test

```typescript import {mapObjIndexed} from 'rambda' const obj = {a: 1, b: 2, c: 3} describe('R.mapObjIndexed', () => { it('without type transform', () => { const result = mapObjIndexed((x, prop, obj) => { x // $ExpectType number prop // $ExpectType string obj // $ExpectType Dictionary return x + 2 }, obj) result // $ExpectType Dictionary }) it('without type transform - curried', () => { const result = mapObjIndexed((x, prop, obj) => { x // $ExpectType number prop // $ExpectType string obj // $ExpectType Dictionary return x + 2 })(obj) result // $ExpectType Dictionary }) it('change of type', () => { const result = mapObjIndexed((x, prop, obj) => { x // $ExpectType number prop // $ExpectType string obj // $ExpectType Dictionary return String(x + 2) }, obj) result // $ExpectType Dictionary }) it('change of type - curried', () => { const result = mapObjIndexed((x, prop, obj) => { x // $ExpectType number prop // $ExpectType string obj // $ExpectType Dictionary return String(x + 2) })(obj) result // $ExpectType Dictionary }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#mapObjIndexed) ### match ```typescript match(regExpression: RegExp, str: string): string[] ``` Curried version of `String.prototype.match` which returns empty array, when there is no match. Try this R.match example in Rambda REPL

All Typescript definitions

```typescript match(regExpression: RegExp, str: string): string[]; match(regExpression: RegExp): (str: string) => string[]; ```

R.match source

```javascript export function match(pattern, input){ if (arguments.length === 1) return _input => match(pattern, _input) const willReturn = input.match(pattern) return willReturn === null ? [] : willReturn } ```

Tests

```javascript import { equals } from './equals.js' import { match } from './match.js' test('happy', () => { expect(match(/a./g)('foo bar baz')).toEqual([ 'ar', 'az' ]) }) test('fallback', () => { expect(match(/a./g)('foo')).toEqual([]) }) test('with string', () => { expect(match('a', 'foo')).toEqual([]) expect(equals(match('o', 'foo'), [ 'o' ])).toBeTrue() }) test('throwing', () => { expect(() => { match(/a./g, null) }).toThrowErrorMatchingInlineSnapshot('"Cannot read properties of null (reading \'match\')"') }) ```

Typescript test

```typescript import {match} from 'rambda' const str = 'foo bar' describe('R.match', () => { it('happy', () => { const result = match(/foo/, str) result // $ExpectType string[] }) it('curried', () => { const result = match(/foo/)(str) result // $ExpectType string[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#match) ### mathMod `R.mathMod` behaves like the modulo operator should mathematically, unlike the `%` operator (and by extension, `R.modulo`). So while `-17 % 5` is `-2`, `mathMod(-17, 5)` is `3`. Try this R.mathMod example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#mathMod) ### max It returns the greater value between `x` and `y`. Try this R.max example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#max) ### maxBy It returns the greater value between `x` and `y` according to `compareFn` function. Try this R.maxBy example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#maxBy) ### mean ```typescript mean(list: number[]): number ``` It returns the mean value of `list` input. Try this R.mean example in Rambda REPL

All Typescript definitions

```typescript mean(list: number[]): number; ```

R.mean source

```javascript import { sum } from './sum.js' export function mean(list){ return sum(list) / list.length } ```

Tests

```javascript import { mean } from './mean.js' test('happy', () => { expect(mean([ 2, 7 ])).toBe(4.5) }) test('with NaN', () => { expect(mean([])).toBeNaN() }) ```

Typescript test

```typescript import {mean} from 'rambda' describe('R.mean', () => { it('happy', () => { const result = mean([1, 2, 3]) result // $ExpectType number }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#mean) ### median ```typescript median(list: number[]): number ``` It returns the median value of `list` input. Try this R.median example in Rambda REPL

All Typescript definitions

```typescript median(list: number[]): number; ```

R.median source

```javascript import { mean } from './mean.js' export function median(list){ const len = list.length if (len === 0) return NaN const width = 2 - len % 2 const idx = (len - width) / 2 return mean(Array.prototype.slice .call(list, 0) .sort((a, b) => { if (a === b) return 0 return a < b ? -1 : 1 }) .slice(idx, idx + width)) } ```

Tests

```javascript import { median } from './median.js' test('happy', () => { expect(median([ 2 ])).toBe(2) expect(median([ 7, 2, 10, 2, 9 ])).toBe(7) }) test('with empty array', () => { expect(median([])).toBeNaN() }) ```

Typescript test

```typescript import {median} from 'rambda' describe('R.median', () => { it('happy', () => { const result = median([1, 2, 3]) result // $ExpectType number }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#median) ### merge Same as `R.mergeRight`. [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#merge) ### mergeAll ```typescript mergeAll(list: object[]): T ``` It merges all objects of `list` array sequentially and returns the result. Try this R.mergeAll example in Rambda REPL

All Typescript definitions

```typescript mergeAll(list: object[]): T; mergeAll(list: object[]): object; ```

R.mergeAll source

```javascript import { map } from './map.js' import { mergeRight } from './mergeRight.js' export function mergeAll(arr){ let willReturn = {} map(val => { willReturn = mergeRight(willReturn, val) }, arr) return willReturn } ```

Tests

```javascript import { mergeAll } from './mergeAll.js' test('case 1', () => { const arr = [ { a : 1 }, { b : 2 }, { c : 3 } ] const expectedResult = { a : 1, b : 2, c : 3, } expect(mergeAll(arr)).toEqual(expectedResult) }) test('case 2', () => { expect(mergeAll([ { foo : 1 }, { bar : 2 }, { baz : 3 } ])).toEqual({ foo : 1, bar : 2, baz : 3, }) }) ```

Typescript test

```typescript import {mergeAll} from 'rambda' describe('R.mergeAll', () => { it('with passing type', () => { interface Output { foo: number, bar: number, } const result = mergeAll([{foo: 1}, {bar: 2}]) result.foo // $ExpectType number result.bar // $ExpectType number }) it('without passing type', () => { const result = mergeAll([{foo: 1}, {bar: 2}]) result // $ExpectType unknown }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#mergeAll) ### mergeDeepRight ```typescript mergeDeepRight(target: object, newProps: object): Output ``` Creates a new object with the own properties of the first object merged with the own properties of the second object. If a key exists in both objects: - and both values are objects, the two values will be recursively merged - otherwise the value from the second object will be used.

All Typescript definitions

```typescript mergeDeepRight(target: object, newProps: object): Output; mergeDeepRight(target: object): (newProps: object) => Output; ```

R.mergeDeepRight source

```javascript import { clone } from './clone.js' import { type } from './type.js' export function mergeDeepRight(target, source){ if (arguments.length === 1){ return sourceHolder => mergeDeepRight(target, sourceHolder) } const willReturn = clone(target) Object.keys(source).forEach(key => { if (type(source[ key ]) === 'Object'){ if (type(target[ key ]) === 'Object'){ willReturn[ key ] = mergeDeepRight(target[ key ], source[ key ]) } else { willReturn[ key ] = source[ key ] } } else { willReturn[ key ] = source[ key ] } }) return willReturn } ```

Tests

```javascript import { mergeDeepRight } from './mergeDeepRight.js' const student = { name : 'foo', age : 10, contact : { a : 1, email : 'foo@example.com', }, } const teacher = { age : 40, contact : { email : 'baz@example.com' }, songs : { title : 'Remains the same' }, } test('when merging object with lists inside them', () => { const a = { a : [ 1, 2, 3 ], b : [ 4, 5, 6 ], } const b = { a : [ 7, 8, 9 ], b : [ 10, 11, 12 ], } const result = mergeDeepRight(a, b) const expected = { a : [ 7, 8, 9 ], b : [ 10, 11, 12 ], } expect(result).toEqual(expected) }) test('happy', () => { const result = mergeDeepRight(student, teacher) const curryResult = mergeDeepRight(student)(teacher) const expected = { age : 40, name : 'foo', contact : { a : 1, email : 'baz@example.com', }, songs : { title : 'Remains the same' }, } expect(result).toEqual(expected) expect(curryResult).toEqual(expected) }) test('issue 650', () => { expect(Object.keys(mergeDeepRight({ a : () => {} }, { b : () => {} }))).toEqual([ 'a', 'b', ]) }) test('ramda compatible test 1', () => { const a = { w : 1, x : 2, y : { z : 3 }, } const b = { a : 4, b : 5, c : { d : 6 }, } const result = mergeDeepRight(a, b) const expected = { w : 1, x : 2, y : { z : 3 }, a : 4, b : 5, c : { d : 6 }, } expect(result).toEqual(expected) }) test('ramda compatible test 2', () => { const a = { a : { b : 1, c : 2, }, y : 0, } const b = { a : { b : 3, d : 4, }, z : 0, } const result = mergeDeepRight(a, b) const expected = { a : { b : 3, c : 2, d : 4, }, y : 0, z : 0, } expect(result).toEqual(expected) }) test('ramda compatible test 3', () => { const a = { w : 1, x : { y : 2 }, } const result = mergeDeepRight(a, { x : { y : 3 } }) const expected = { w : 1, x : { y : 3 }, } expect(result).toEqual(expected) }) test('functions are not discarded', () => { const obj = { foo : () => {} } expect(typeof mergeDeepRight(obj, {}).foo).toBe('function') }) ```

Typescript test

```typescript import {mergeDeepRight} from 'rambda' interface Output { foo: { bar: number, }, } describe('R.mergeDeepRight', () => { const result = mergeDeepRight({foo: {bar: 1}}, {foo: {bar: 2}}) result.foo.bar // $ExpectType number }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#mergeDeepRight) ### mergeLeft ```typescript mergeLeft(newProps: object, target: object): Output ``` Same as `R.merge`, but in opposite direction. Try this R.mergeLeft example in Rambda REPL

All Typescript definitions

```typescript mergeLeft(newProps: object, target: object): Output; mergeLeft(newProps: object): (target: object) => Output; ```

R.mergeLeft source

```javascript import { mergeRight } from './mergeRight.js' export function mergeLeft(x, y){ if (arguments.length === 1) return _y => mergeLeft(x, _y) return mergeRight(y, x) } ```

Tests

```javascript import { mergeLeft } from './mergeLeft.js' const obj = { foo : 1, bar : 2, } test('happy', () => { expect(mergeLeft({ bar : 20 }, obj)).toEqual({ foo : 1, bar : 20, }) }) test('curry', () => { expect(mergeLeft({ baz : 3 })(obj)).toEqual({ foo : 1, bar : 2, baz : 3, }) }) test('when undefined or null instead of object', () => { expect(mergeLeft(null, undefined)).toEqual({}) expect(mergeLeft(obj, null)).toEqual(obj) expect(mergeLeft(obj, undefined)).toEqual(obj) expect(mergeLeft(undefined, obj)).toEqual(obj) }) ```

Typescript test

```typescript import {mergeLeft} from 'rambda' interface Output { foo: number, bar: number, } describe('R.mergeLeft', () => { const result = mergeLeft({foo: 1}, {bar: 2}) const curriedResult = mergeLeft({foo: 1})({bar: 2}) result.foo // $ExpectType number result.bar // $ExpectType number curriedResult.bar // $ExpectType number }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#mergeLeft) ### mergeRight It creates a copy of `target` object with overwritten `newProps` properties. Previously known as `R.merge` but renamed after Ramda did the same. Try this R.mergeRight example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#mergeRight) ### mergeWith ```typescript mergeWith(fn: (x: any, z: any) => any, a: Record, b: Record): Record ``` It takes two objects and a function, which will be used when there is an overlap between the keys. Try this R.mergeWith example in Rambda REPL

All Typescript definitions

```typescript mergeWith(fn: (x: any, z: any) => any, a: Record, b: Record): Record; mergeWith(fn: (x: any, z: any) => any, a: Record, b: Record): Output; mergeWith(fn: (x: any, z: any) => any, a: Record): (b: Record) => Record; mergeWith(fn: (x: any, z: any) => any, a: Record): (b: Record) => Output; mergeWith(fn: (x: any, z: any) => any): (a: U, b: V) => Record; mergeWith(fn: (x: any, z: any) => any): (a: U, b: V) => Output; ```

R.mergeWith source

```javascript import { curry } from './curry.js' function mergeWithFn( mergeFn, a, b ){ const willReturn = {} Object.keys(a).forEach(key => { if (b[ key ] === undefined){ willReturn[ key ] = a[ key ] } else { willReturn[ key ] = mergeFn(a[ key ], b[ key ]) } }) Object.keys(b).forEach(key => { if (willReturn[ key ] !== undefined) return if (a[ key ] === undefined){ willReturn[ key ] = b[ key ] } else { willReturn[ key ] = mergeFn(a[ key ], b[ key ]) } }) return willReturn } export const mergeWith = curry(mergeWithFn) ```

Tests

```javascript import { concat } from './concat.js' import { mergeWith } from './mergeWith.js' test('happy', () => { const result = mergeWith( concat, { a : true, values : [ 10, 20 ], }, { b : true, values : [ 15, 35 ], } ) const expected = { a : true, values : [ 10, 20, 15, 35 ], b : true, } expect(result).toEqual(expected) }) ```

Typescript test

```typescript import {concat, mergeWith} from 'rambda' interface Output { a: boolean, b: boolean, values: number[], } const A = { a: true, values: [10, 20], } const B = { b: true, values: [15, 35], } describe('R.mergeWith', () => { test('no curry | without explicit types', () => { const result = mergeWith(concat, A, B) result // $ExpectType Record }) test('no curry | with explicit types', () => { const result = mergeWith(concat, A, B) result // $ExpectType Output }) test('curry 1 | without explicit types', () => { const result = mergeWith(concat, A)(B) result // $ExpectType Record }) test('curry 1 | with explicit types', () => { const result = mergeWith(concat, A)(B) result // $ExpectType Output }) test('curry 2 | without explicit types', () => { const result = mergeWith(concat)(A, B) result // $ExpectType Record }) test('curry 2 | with explicit types', () => { const result = mergeWith(concat)(A, B) result // $ExpectType Output }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#mergeWith) ### min It returns the lesser value between `x` and `y`. Try this R.min example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#min) ### minBy It returns the lesser value between `x` and `y` according to `compareFn` function. Try this R.minBy example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#minBy) ### modify ```typescript modify( prop: K, fn: (a: T[K]) => P, obj: T, ): Omit & Record ``` Try this R.modify example in Rambda REPL

All Typescript definitions

```typescript modify( prop: K, fn: (a: T[K]) => P, obj: T, ): Omit & Record; modify( prop: K, fn: (a: A) => P, ): >(target: T) => Omit & Record; ```

R.modify source

```javascript import { isArray } from './_internals/isArray.js' import { isIterable } from './_internals/isIterable.js' import { curry } from './curry.js' import { updateFn } from './update.js' function modifyFn( property, fn, iterable ){ if (!isIterable(iterable)) return iterable if (iterable[ property ] === undefined) return iterable if (isArray(iterable)){ return updateFn( property, fn(iterable[ property ]), iterable ) } return { ...iterable, [ property ] : fn(iterable[ property ]), } } export const modify = curry(modifyFn) ```

Tests

```javascript import { modify as modifyRamda } from 'ramda' import { compareCombinations, FALSY_VALUES } from './_internals/testUtils.js' import { add } from './add.js' import { compose } from './compose.js' import { modify } from './modify.js' const person = { name : 'foo', age : 20, } test('happy', () => { expect(modify( 'age', x => x + 1, person )).toEqual({ name : 'foo', age : 21, }) }) test('property is missing', () => { expect(modify( 'foo', x => x + 1, person )).toEqual(person) }) test('adjust if `array` at the given key with the `transformation` function', () => { expect(modify( 1, add(1), [ 100, 1400 ] )).toEqual([ 100, 1401 ]) }) describe('ignores transformations if the input value is not Array and Object', () => { ;[ 42, undefined, null, '' ].forEach(value => { it(`${ value }`, () => { expect(modify( 'a', add(1), value )).toEqual(value) }) }) }) const possibleProperties = [ ...FALSY_VALUES, 'foo', 0 ] const possibleTransformers = [ ...FALSY_VALUES, add(1), add('foo'), compose, String, ] const possibleObjects = [ ...FALSY_VALUES, {}, [ 1, 2, 3 ], { a : 1, foo : 2, }, { a : 1, foo : [ 1 ], }, { a : 1, foo : 'bar', }, ] describe('brute force', () => { compareCombinations({ fn : modify, fnRamda : modifyRamda, firstInput : possibleProperties, secondInput : possibleTransformers, thirdInput : possibleObjects, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 0, "RESULTS_MISMATCH": 0, "SHOULD_NOT_THROW": 0, "SHOULD_THROW": 0, "TOTAL_TESTS": 630, } `) }, }) }) ```

Typescript test

```typescript import {modify, add} from 'rambda' const person = {name: 'James', age: 20} describe('R.modify', () => { it('happy', () => { const {age} = modify('age', add(1), person) const {age: ageAsString} = modify('age', String, person) age // $ExpectType number ageAsString // $ExpectType string }) it('curried', () => { const {age} = modify('age', add(1))(person) age // $ExpectType number }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#modify) ### modifyPath ```typescript modifyPath>(path: Path, fn: (x: any) => unknown, object: Record): T ``` It changes a property of object on the base of provided path and transformer function. Try this R.modifyPath example in Rambda REPL

All Typescript definitions

```typescript modifyPath>(path: Path, fn: (x: any) => unknown, object: Record): T; modifyPath>(path: Path, fn: (x: any) => unknown): (object: Record) => T; modifyPath>(path: Path): (fn: (x: any) => unknown) => (object: Record) => T; ```

R.modifyPath source

```javascript import { createPath } from './_internals/createPath.js' import { isArray } from './_internals/isArray.js' import { assoc } from './assoc.js' import { curry } from './curry.js' import { path as pathModule } from './path.js' export function modifyPathFn( pathInput, fn, object ){ const path = createPath(pathInput) if (path.length === 1){ return { ...object, [ path[ 0 ] ] : fn(object[ path[ 0 ] ]), } } if (pathModule(path, object) === undefined) return object const val = modifyPath( Array.prototype.slice.call(path, 1), fn, object[ path[ 0 ] ] ) if (val === object[ path[ 0 ] ]){ return object } return assoc( path[ 0 ], val, object ) } export const modifyPath = curry(modifyPathFn) ```

Tests

```javascript import { modifyPath } from './modifyPath.js' test('happy', () => { const result = modifyPath( 'a.b.c', x => x + 1, { a : { b : { c : 1 } } } ) expect(result).toEqual({ a : { b : { c : 2 } } }) }) test('with array', () => { const input = { foo : [ { bar : '123' } ] } const result = modifyPath( 'foo.0.bar', x => x + 'foo', input ) expect(result).toEqual({ foo : { 0 : { bar : '123foo' } } }) }) ```

Typescript test

```typescript import {modifyPath} from 'rambda' const obj = {a: {b: {c: 1}}} describe('R.modifyPath', () => { it('happy', () => { const result = modifyPath('a.b.c', (x: number) => x + 1, obj) result // $ExpectType Record }) it('explicit return type', () => { interface Foo extends Record { a: 1, } const result = modifyPath('a.b.c', (x: number) => x + 1, obj) result // $ExpectType Foo }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#modifyPath) ### modulo Curried version of `x%y`. Try this R.modulo example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#modulo) ### move It returns a copy of `list` with exchanged `fromIndex` and `toIndex` elements. Try this R.move example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#move) ### multiply Curried version of `x*y`. Try this R.multiply example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#multiply) ### negate Try this R.negate example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#negate) ### none ```typescript none(predicate: (x: T) => boolean, list: T[]): boolean ``` It returns `true`, if all members of array `list` returns `false`, when applied as argument to `predicate` function. Try this R.none example in Rambda REPL

All Typescript definitions

```typescript none(predicate: (x: T) => boolean, list: T[]): boolean; none(predicate: (x: T) => boolean): (list: T[]) => boolean; ```

R.none source

```javascript export function none(predicate, list){ if (arguments.length === 1) return _list => none(predicate, _list) for (let i = 0; i < list.length; i++){ if (predicate(list[ i ])) return false } return true } ```

Tests

```javascript import { none } from './none.js' const isEven = n => n % 2 === 0 test('when true', () => { expect(none(isEven, [ 1, 3, 5, 7 ])).toBeTrue() }) test('when false curried', () => { expect(none(input => input > 1, [ 1, 2, 3 ])).toBeFalse() }) ```

Typescript test

```typescript import {none} from 'rambda' describe('R.none', () => { it('happy', () => { const result = none( x => { x // $ExpectType number return x > 0 }, [1, 2, 3] ) result // $ExpectType boolean }) it('curried needs a type', () => { const result = none(x => { x // $ExpectType number return x > 0 })([1, 2, 3]) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#none) ### nop ```typescript nop(): void ``` It returns `undefined`. Try this R.nop example in Rambda REPL

All Typescript definitions

```typescript nop(): void; ```

R.nop source

```javascript export function nop(){} ```

Tests

```javascript import { nop } from './nop.js' test('call', () => { expect(nop).not.toThrow() }) ```

Typescript test

```typescript import {nop} from 'rambda' describe('R.nop', () => { it('call', () => { const result = nop() result // $ExpectType void }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#nop) ### not ```typescript not(input: any): boolean ``` It returns a boolean negated version of `input`. Try this R.not example in Rambda REPL

All Typescript definitions

```typescript not(input: any): boolean; ```

R.not source

```javascript export function not(input){ return !input } ```

Tests

```javascript import { not } from './not.js' test('not', () => { expect(not(false)).toBeTrue() expect(not(true)).toBeFalse() expect(not(0)).toBeTrue() expect(not(1)).toBeFalse() }) ```

Typescript test

```typescript import {not} from 'rambda' describe('R.not', () => { it('happy', () => { const result = not(4) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#not) ### nth ```typescript nth(index: number, input: string): string ``` Curried version of `input[index]`. Try this R.nth example in Rambda REPL

All Typescript definitions

```typescript nth(index: number, input: string): string; nth(index: number, input: T[]): T | undefined; nth(n: number): { (input: T[]): T | undefined; (input: string): string; }; ```

R.nth source

```javascript export function nth(index, input){ if (arguments.length === 1) return _input => nth(index, _input) const idx = index < 0 ? input.length + index : index return Object.prototype.toString.call(input) === '[object String]' ? input.charAt(idx) : input[ idx ] } ```

Tests

```javascript import { nth } from './nth.js' test('happy', () => { expect(nth(2, [ 1, 2, 3, 4 ])).toBe(3) }) test('with curry', () => { expect(nth(2)([ 1, 2, 3, 4 ])).toBe(3) }) test('with string and correct index', () => { expect(nth(2)('foo')).toBe('o') }) test('with string and invalid index', () => { expect(nth(20)('foo')).toBe('') }) test('with negative index', () => { expect(nth(-3)([ 1, 2, 3, 4 ])).toBe(2) }) ```

Typescript test

```typescript import {nth} from 'rambda' const list = [1, 2, 3] describe('R.nth', () => { it('happy', () => { const result = nth(4, list) result // $ExpectType number | undefined }) it('curried', () => { const result = nth(1)(list) result // $ExpectType number | undefined }) }) describe('R.nth - string', () => { const str = 'abc' it('happy', () => { const result = nth(4, str) result // $ExpectType string }) it('curried', () => { const result = nth(1)(str) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#nth) ### objOf It creates an object with a single key-value pair. Try this R.objOf example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#objOf) ### of ```typescript of(x: T): T[] ``` Try this R.of example in Rambda REPL

All Typescript definitions

```typescript of(x: T): T[]; ```

R.of source

```javascript export function of(value){ return [ value ] } ```

Tests

```javascript import { of } from './of.js' test('happy', () => { expect(of(3)).toEqual([ 3 ]) expect(of(null)).toEqual([ null ]) }) ```

Typescript test

```typescript import {of} from 'rambda' const list = [1, 2, 3] describe('R.of', () => { it('happy', () => { const result = of(4) result // $ExpectType number[] }) it('curried', () => { const result = of(list) result // $ExpectType number[][] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#of) ### omit ```typescript omit(propsToOmit: K[], obj: T): Omit ``` It returns a partial copy of an `obj` without `propsToOmit` properties. Try this R.omit example in Rambda REPL

All Typescript definitions

```typescript omit(propsToOmit: K[], obj: T): Omit; omit(propsToOmit: K[]): (obj: T) => Omit; omit(propsToOmit: string, obj: T): U; omit(propsToOmit: string): (obj: T) => U; omit(propsToOmit: string, obj: object): T; omit(propsToOmit: string): (obj: object) => T; ```

R.omit source

```javascript import { createPath } from './_internals/createPath.js' export function omit(propsToOmit, obj){ if (arguments.length === 1) return _obj => omit(propsToOmit, _obj) if (obj === null || obj === undefined){ return undefined } const propsToOmitValue = createPath(propsToOmit, ',') const willReturn = {} for (const key in obj){ if (!propsToOmitValue.includes(key)){ willReturn[ key ] = obj[ key ] } } return willReturn } ```

Tests

```javascript import { omit } from './omit.js' test('with string as condition', () => { const obj = { a : 1, b : 2, c : 3, } const result = omit('a,c', obj) const resultCurry = omit('a,c')(obj) const expectedResult = { b : 2 } expect(result).toEqual(expectedResult) expect(resultCurry).toEqual(expectedResult) }) test('with null', () => { expect(omit('a,b', null)).toBeUndefined() }) test('doesn\'t work with number as property', () => { expect(omit([ 42 ], { a : 1, 42 : 2, })).toEqual({ 42 : 2, a : 1, }) }) test('happy', () => { expect(omit([ 'a', 'c' ])({ a : 'foo', b : 'bar', c : 'baz', })).toEqual({ b : 'bar' }) }) ```

Typescript test

```typescript import {omit} from 'rambda' describe('R.omit with array as props input', () => { it('allow Typescript to infer object type', () => { const input = {a: 'foo', b: 2, c: 3, d: 4} const result = omit(['b,c'], input) result.a // $ExpectType string result.d // $ExpectType number const curriedResult = omit(['a,c'], input) curriedResult.a // $ExpectType string curriedResult.d // $ExpectType number }) it('declare type of input object', () => { interface Input { a: string, b: number, c: number, d: number, } const input: Input = {a: 'foo', b: 2, c: 3, d: 4} const result = omit(['b,c'], input) result // $ExpectType Omit result.a // $ExpectType string result.d // $ExpectType number const curriedResult = omit(['a,c'], input) curriedResult.a // $ExpectType string curriedResult.d // $ExpectType number }) }) describe('R.omit with string as props input', () => { interface Output { b: number, d: number, } it('explicitly declare output', () => { const result = omit('a,c', {a: 1, b: 2, c: 3, d: 4}) result // $ExpectType Output result.b // $ExpectType number const curriedResult = omit('a,c')({a: 1, b: 2, c: 3, d: 4}) curriedResult.b // $ExpectType number }) it('explicitly declare input and output', () => { interface Input { a: number, b: number, c: number, d: number, } const result = omit('a,c', {a: 1, b: 2, c: 3, d: 4}) result // $ExpectType Output result.b // $ExpectType number const curriedResult = omit('a,c')({ a: 1, b: 2, c: 3, d: 4, }) curriedResult.b // $ExpectType number }) it('without passing type', () => { const result = omit('a,c', {a: 1, b: 2, c: 3, d: 4}) result // $ExpectType unknown }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#omit) ### on It passes the two inputs through `unaryFn` and then the results are passed as inputs the the `binaryFn` to receive the final result(`binaryFn(unaryFn(FIRST_INPUT), unaryFn(SECOND_INPUT))`). This method is also known as P combinator. Try this R.on example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#on) ### once ```typescript once(func: T): T ``` It returns a function, which invokes only once `fn` function. Try this R.once example in Rambda REPL

All Typescript definitions

```typescript once(func: T): T; ```

R.once source

```javascript import { curry } from './curry.js' function onceFn(fn, context){ let result return function (){ if (fn){ result = fn.apply(context || this, arguments) fn = null } return result } } export function once(fn, context){ if (arguments.length === 1){ const wrap = onceFn(fn, context) return curry(wrap) } return onceFn(fn, context) } ```

Tests

```javascript import { once } from './once.js' test('with counter', () => { let counter = 0 const runOnce = once(x => { counter++ return x + 2 }) expect(runOnce(1)).toBe(3) runOnce(1) runOnce(1) runOnce(1) expect(counter).toBe(1) }) test('happy path', () => { const addOneOnce = once(( a, b, c ) => a + b + c, 1) expect(addOneOnce( 10, 20, 30 )).toBe(60) expect(addOneOnce(40)).toBe(60) }) ```

Typescript test

```typescript import {once} from 'rambda' describe('R.once', () => { it('happy', () => { const runOnce = once((x: number) => { return x + 2 }) const result = runOnce(1) result // $ExpectType number }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#once) ### or Logical OR Try this R.or example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#or) ### over ```typescript over(lens: Lens, fn: Arity1Fn, value: T): T ``` It returns a copied **Object** or **Array** with modified value received by applying function `fn` to `lens` focus. Try this R.over example in Rambda REPL

All Typescript definitions

```typescript over(lens: Lens, fn: Arity1Fn, value: T): T; over(lens: Lens, fn: Arity1Fn, value: T[]): T[]; over(lens: Lens, fn: Arity1Fn): (value: T) => T; over(lens: Lens, fn: Arity1Fn): (value: T[]) => T[]; over(lens: Lens): (fn: Arity1Fn, value: T) => T; over(lens: Lens): (fn: Arity1Fn, value: T[]) => T[]; ```

R.over source

```javascript import { curry } from './curry.js' const Identity = x => ({ x, map : fn => Identity(fn(x)), }) function overFn( lens, fn, object ){ return lens(x => Identity(fn(x)))(object).x } export const over = curry(overFn) ```

Tests

```javascript import { assoc } from './assoc.js' import { lens } from './lens.js' import { lensIndex } from './lensIndex.js' import { lensPath } from './lensPath.js' import { over } from './over.js' import { prop } from './prop.js' import { toUpper } from './toUpper.js' const testObject = { foo : 'bar', baz : { a : 'x', b : 'y', }, } test('assoc lens', () => { const assocLens = lens(prop('foo'), assoc('foo')) const result = over( assocLens, toUpper, testObject ) const expected = { ...testObject, foo : 'BAR', } expect(result).toEqual(expected) }) test('path lens', () => { const pathLens = lensPath('baz.a') const result = over( pathLens, toUpper, testObject ) const expected = { ...testObject, baz : { a : 'X', b : 'y', }, } expect(result).toEqual(expected) }) test('index lens', () => { const indexLens = lensIndex(0) const result = over(indexLens, toUpper)([ 'foo', 'bar' ]) expect(result).toEqual([ 'FOO', 'bar' ]) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#over) ### partial ```typescript partial(fn: (x0: V0, x1: V1) => T, args: [V0]): (x1: V1) => T ``` It is very similar to `R.curry`, but you can pass initial arguments when you create the curried function. `R.partial` will keep returning a function until all the arguments that the function `fn` expects are passed. The name comes from the fact that you partially inject the inputs. Try this R.partial example in Rambda REPL

All Typescript definitions

```typescript partial(fn: (x0: V0, x1: V1) => T, args: [V0]): (x1: V1) => T; partial(fn: (x0: V0, x1: V1, x2: V2) => T, args: [V0, V1]): (x2: V2) => T; partial(fn: (x0: V0, x1: V1, x2: V2) => T, args: [V0]): (x1: V1, x2: V2) => T; partial(fn: (x0: V0, x1: V1, x2: V2, x3: V3) => T, args: [V0, V1, V2]): (x2: V3) => T; partial(fn: (x0: V0, x1: V1, x2: V2, x3: V3) => T, args: [V0, V1]): (x2: V2, x3: V3) => T; partial(fn: (x0: V0, x1: V1, x2: V2, x3: V3) => T, args: [V0]): (x1: V1, x2: V2, x3: V3) => T; partial(fn: (...a: any[]) => T, args: any[]): (...x: any[]) => T; ```

R.partial source

```javascript export function partial(fn, ...args){ const len = fn.length return (...rest) => { if (args.length + rest.length >= len){ return fn(...args, ...rest) } return partial(fn, ...[ ...args, ...rest ]) } } ```

Tests

```javascript import { partial } from './partial.js' import { type } from './type.js' const greet = ( salutation, title, firstName, lastName ) => salutation + ', ' + title + ' ' + firstName + ' ' + lastName + '!' test('happy', () => { const canPassAnyNumberOfArguments = partial( greet, 'Hello', 'Ms.' ) const fn = canPassAnyNumberOfArguments('foo') const sayHello = partial(greet, [ 'Hello' ]) const sayHelloRamda = partial(sayHello, [ 'Ms.' ]) expect(type(fn)).toBe('Function') expect(fn('bar')).toBe('Hello, Ms. foo bar!') expect(sayHelloRamda('foo', 'bar')).toBe('Hello, Ms. foo bar!') }) test('extra arguments are ignored', () => { const canPassAnyNumberOfArguments = partial( greet, 'Hello', 'Ms.' ) const fn = canPassAnyNumberOfArguments('foo') expect(type(fn)).toBe('Function') expect(fn( 'bar', 1, 2 )).toBe('Hello, Ms. foo bar!') }) test('when array is input', () => { const fooFn = ( a, b, c, d ) => ({ a, b, c, d, }) const barFn = partial( fooFn, [ 1, 2 ], [] ) expect(barFn(1, 2)).toEqual({ a : [ 1, 2 ], b : [], c : 1, d : 2, }) }) test('ramda spec', () => { const sayHello = partial(greet, 'Hello') const sayHelloToMs = partial(sayHello, 'Ms.') expect(sayHelloToMs('Jane', 'Jones')).toBe('Hello, Ms. Jane Jones!') }) ```

Typescript test

```typescript import {partial} from 'rambda' describe('R.partial', () => { it('happy', () => { function greet( salutation: string, title: string, firstName: string, lastName: string ) { return `${salutation}, ${title} ${firstName} ${lastName}!` } const sayHello = partial(greet, ['Hello']) const sayHelloToMs = partial(sayHello, ['Ms.']) const result = sayHelloToMs('Jane', 'Jones') result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#partial) ### partialObject ```typescript partialObject( fn: (input: Input) => Output, partialInput: PartialInput, ): (input: Pick>) => Output ``` `R.partialObject` is a curry helper designed specifically for functions accepting object as a single argument. Initially the function knows only a part from the whole input object and then `R.partialObject` helps in preparing the function for the second part, when it receives the rest of the input. Try this R.partialObject example in Rambda REPL

All Typescript definitions

```typescript partialObject( fn: (input: Input) => Output, partialInput: PartialInput, ): (input: Pick>) => Output; ```

R.partialObject source

```javascript import { mergeDeepRight } from './mergeDeepRight.js' export function partialObject(fn, input){ return nextInput => fn(mergeDeepRight(nextInput, input)) } ```

Tests

```javascript import { delay } from './delay.js' import { partialObject } from './partialObject.js' import { type } from './type.js' test('with plain function', () => { const fn = ({ a, b, c }) => a + b + c const curried = partialObject(fn, { a : 1 }) expect(type(curried)).toBe('Function') expect(curried({ b : 2, c : 3, })).toBe(6) }) test('with function that throws an error', () => { const fn = ({ a, b, c }) => { throw new Error('foo') } const curried = partialObject(fn, { a : 1 }) expect(type(curried)).toBe('Function') expect(() => curried({ b : 2, c : 3, })).toThrowErrorMatchingInlineSnapshot('"foo"') }) test('with async', async () => { const fn = async ({ a, b, c }) => { await delay(100) return a + b + c } const curried = partialObject(fn, { a : 1 }) const result = await curried({ b : 2, c : 3, }) expect(result).toBe(6) }) test('async function throwing an error', async () => { const fn = async ({ a, b, c }) => { await delay(100) throw new Error('foo') } const curried = partialObject(fn, { a : 1 }) try { await curried({ b : 2, c : 3, }) expect(true).toBeFalsy() } catch (e){ expect(e.message).toBe('foo') } }) ```

Typescript test

```typescript import {partialObject, delay} from 'rambda' describe('R.partialObject', () => { it('happy', () => { interface Input { a: number, b: number, c: string, } const fn = ({a, b, c}: Input) => a + b + c const curried = partialObject(fn, {a: 1}) const result = curried({ b: 2, c: 'foo', }) result // $ExpectType string }) it('asynchronous', async() => { interface Input { a: number, b: number, c: string, } const fn = async({a, b, c}: Input) => { await delay(100) return a + b + c } const curried = partialObject(fn, {a: 1}) const result = await curried({ b: 2, c: 'foo', }) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#partialObject) ### partition ```typescript partition( predicate: Predicate, input: T[] ): [T[], T[]] ``` It will return array of two objects/arrays according to `predicate` function. The first member holds all instances of `input` that pass the `predicate` function, while the second member - those who doesn't. Try this R.partition example in Rambda REPL

All Typescript definitions

```typescript partition( predicate: Predicate, input: T[] ): [T[], T[]]; partition( predicate: Predicate ): (input: T[]) => [T[], T[]]; partition( predicate: (x: T, prop?: string) => boolean, input: { [key: string]: T} ): [{ [key: string]: T}, { [key: string]: T}]; partition( predicate: (x: T, prop?: string) => boolean ): (input: { [key: string]: T}) => [{ [key: string]: T}, { [key: string]: T}]; ```

R.partition source

```javascript import { isArray } from './_internals/isArray.js' export function partitionObject(predicate, iterable){ const yes = {} const no = {} Object.entries(iterable).forEach(([ prop, value ]) => { if (predicate(value, prop)){ yes[ prop ] = value } else { no[ prop ] = value } }) return [ yes, no ] } export function partitionArray( predicate, list, indexed = false ){ const yes = [] const no = [] let counter = -1 while (counter++ < list.length - 1){ if ( indexed ? predicate(list[ counter ], counter) : predicate(list[ counter ]) ){ yes.push(list[ counter ]) } else { no.push(list[ counter ]) } } return [ yes, no ] } export function partition(predicate, iterable){ if (arguments.length === 1){ return listHolder => partition(predicate, listHolder) } if (!isArray(iterable)) return partitionObject(predicate, iterable) return partitionArray(predicate, iterable) } ```

Tests

```javascript import { partition } from './partition.js' test('with array', () => { const predicate = x => x > 2 const list = [ 1, 2, 3, 4 ] const result = partition(predicate, list) const expectedResult = [ [ 3, 4 ], [ 1, 2 ], ] expect(result).toEqual(expectedResult) }) test('with object', () => { const predicate = (value, prop) => { expect(typeof prop).toBe('string') return value > 2 } const hash = { a : 1, b : 2, c : 3, d : 4, } const result = partition(predicate)(hash) const expectedResult = [ { c : 3, d : 4, }, { a : 1, b : 2, }, ] expect(result).toEqual(expectedResult) }) test('readme example', () => { const list = [ 1, 2, 3 ] const obj = { a : 1, b : 2, c : 3, } const predicate = x => x > 2 const result = [ partition(predicate, list), partition(predicate, obj) ] const expected = [ [ [ 3 ], [ 1, 2 ] ], [ { c : 3 }, { a : 1, b : 2, }, ], ] expect(result).toEqual(expected) }) ```

Typescript test

```typescript import {partition} from 'rambda' describe('R.partition', () => { it('with array', () => { const predicate = (x: number) => { return x > 2 } const list = [1, 2, 3, 4] const result = partition(predicate, list) const curriedResult = partition(predicate)(list) result // $ExpectType [number[], number[]] curriedResult // $ExpectType [number[], number[]] }) /* revert to old version of `dtslint` and `R.partition` typing as there is diff between VSCode types(correct) and dtslint(incorrect) it('with object', () => { const predicate = (value: number, prop?: string) => { return value > 2 } const hash = { a: 1, b: 2, c: 3, d: 4, } const result = partition(predicate, hash) const curriedResult = partition(predicate)(hash) result[0] // $xExpectType { [key: string]: number; } result[1] // $xExpectType { [key: string]: number; } curriedResult[0] // $xExpectType { [key: string]: number; } curriedResult[1] // $xExpectType { [key: string]: number; } }) */ }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#partition) ### path ```typescript path(path: [K0], obj: S): S[K0] ``` If `pathToSearch` is `'a.b'` then it will return `1` if `obj` is `{a:{b:1}}`. It will return `undefined`, if such path is not found. Try this R.path example in Rambda REPL

All Typescript definitions

```typescript path(path: [K0], obj: S): S[K0]; path(path: [K0, K1], obj: S): S[K0][K1]; path< S, K0 extends keyof S = keyof S, K1 extends keyof S[K0] = keyof S[K0], K2 extends keyof S[K0][K1] = keyof S[K0][K1] >(path: [K0, K1, K2], obj: S): S[K0][K1][K2]; path< S, K0 extends keyof S = keyof S, K1 extends keyof S[K0] = keyof S[K0], K2 extends keyof S[K0][K1] = keyof S[K0][K1], K3 extends keyof S[K0][K1][K2] = keyof S[K0][K1][K2], >(path: [K0, K1, K2, K3], obj: S): S[K0][K1][K2][K3]; path< S, K0 extends keyof S = keyof S, K1 extends keyof S[K0] = keyof S[K0], K2 extends keyof S[K0][K1] = keyof S[K0][K1], K3 extends keyof S[K0][K1][K2] = keyof S[K0][K1][K2], K4 extends keyof S[K0][K1][K2][K3] = keyof S[K0][K1][K2][K3], >(path: [K0, K1, K2, K3, K4], obj: S): S[K0][K1][K2][K3][K4]; path< S, K0 extends keyof S = keyof S, K1 extends keyof S[K0] = keyof S[K0], K2 extends keyof S[K0][K1] = keyof S[K0][K1], K3 extends keyof S[K0][K1][K2] = keyof S[K0][K1][K2], K4 extends keyof S[K0][K1][K2][K3] = keyof S[K0][K1][K2][K3], K5 extends keyof S[K0][K1][K2][K3][K4] = keyof S[K0][K1][K2][K3][K4], >(path: [K0, K1, K2, K3, K4, K5], obj: S): S[K0][K1][K2][K3][K4][K5]; path(pathToSearch: string, obj: any): T | undefined; path(pathToSearch: string): (obj: any) => T | undefined; path(pathToSearch: RamdaPath): (obj: any) => T | undefined; path(pathToSearch: RamdaPath, obj: any): T | undefined; ```

R.path source

```javascript import { createPath } from './_internals/createPath.js' export function path(pathInput, obj){ if (arguments.length === 1) return _obj => path(pathInput, _obj) if (obj === null || obj === undefined){ return undefined } let willReturn = obj let counter = 0 const pathArrValue = createPath(pathInput) while (counter < pathArrValue.length){ if (willReturn === null || willReturn === undefined){ return undefined } if (willReturn[ pathArrValue[ counter ] ] === null) return undefined willReturn = willReturn[ pathArrValue[ counter ] ] counter++ } return willReturn } ```

Tests

```javascript import { path } from './path.js' test('with array inside object', () => { const obj = { a : { b : [ 1, { c : 1 } ] } } expect(path('a.b.1.c', obj)).toBe(1) }) test('works with undefined', () => { const obj = { a : { b : { c : 1 } } } expect(path('a.b.c.d.f', obj)).toBeUndefined() expect(path('foo.babaz', undefined)).toBeUndefined() expect(path('foo.babaz')(undefined)).toBeUndefined() }) test('works with string instead of array', () => { expect(path('foo.bar.baz')({ foo : { bar : { baz : 'yes' } } })).toBe('yes') }) test('path', () => { expect(path([ 'foo', 'bar', 'baz' ])({ foo : { bar : { baz : 'yes' } } })).toBe('yes') expect(path([ 'foo', 'bar', 'baz' ])(null)).toBeUndefined() expect(path([ 'foo', 'bar', 'baz' ])({ foo : { bar : 'baz' } })).toBeUndefined() }) test('null is not a valid path', () => { expect(path('audio_tracks', { a : 1, audio_tracks : null, })).toBeUndefined() }) ```

Typescript test

```typescript import {path} from 'rambda' const input = {a: {b: {c: true}}} describe('R.path with string as path', () => { it('without specified output type', () => { // $ExpectType unknown path('a.b.c', input) // $ExpectType unknown path('a.b.c')(input) }) it('with specified output type', () => { // $ExpectType boolean | undefined path('a.b.c', input) // $ExpectType boolean | undefined path('a.b.c')(input) }) }) describe('R.path with list as path', () => { it('with array as path', () => { // $ExpectType boolean path(['a', 'b', 'c'], input) // $ExpectType unknown path(['a', 'b', 'c'])(input) }) test('shallow property', () => { // $ExpectType number path(['a'], {a: 1}) // $ExpectType unknown path(['b'], {a: 1}) }) test('deep property', () => { const testObject = {a: {b: {c: {d: {e: {f: 1}}}}}} const result = path(['a', 'b', 'c', 'd', 'e', 'f'], testObject) // $ExpectType number result const curriedResult = path(['a', 'b', 'c', 'd', 'e', 'f'])(testObject) // $ExpectType unknown curriedResult }) test('issue #668 - path is not correct', () => { const object = { is: { a: 'path', }, } const result = path(['is', 'not', 'a'], object) // $ExpectType unknown result const curriedResult = path(['is', 'not', 'a'])(object) // $ExpectType unknown curriedResult }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#path) ### pathEq ```typescript pathEq(pathToSearch: Path, target: any, input: any): boolean ``` It returns `true` if `pathToSearch` of `input` object is equal to `target` value. `pathToSearch` is passed to `R.path`, which means that it can be either a string or an array. Also equality between `target` and the found value is determined by `R.equals`. Try this R.pathEq example in Rambda REPL

All Typescript definitions

```typescript pathEq(pathToSearch: Path, target: any, input: any): boolean; pathEq(pathToSearch: Path, target: any): (input: any) => boolean; pathEq(pathToSearch: Path): (target: any) => (input: any) => boolean; ```

R.pathEq source

```javascript import { curry } from './curry.js' import { equals } from './equals.js' import { path } from './path.js' function pathEqFn( pathToSearch, target, input ){ return equals(path(pathToSearch, input), target) } export const pathEq = curry(pathEqFn) ```

Tests

```javascript import { pathEq } from './pathEq.js' test('when true', () => { const path = 'a.b' const obj = { a : { b : { c : 1 } } } const target = { c : 1 } expect(pathEq( path, target, obj )).toBeTrue() }) test('when false', () => { const path = 'a.b' const obj = { a : { b : 1 } } const target = 2 expect(pathEq(path, target)(obj)).toBeFalse() }) test('when wrong path', () => { const path = 'foo.bar' const obj = { a : { b : 1 } } const target = 2 expect(pathEq( path, target, obj )).toBeFalse() }) ```

Typescript test

```typescript import {pathEq} from 'rambda' describe('R.pathEq', () => { it('with string path', () => { const pathToSearch = 'a.b.c' const input = {a: {b: {c: 1}}} const target = {c: 1} const result = pathEq(pathToSearch, input, target) const curriedResult = pathEq(pathToSearch, input, target) result // $ExpectType boolean curriedResult // $ExpectType boolean }) it('with array path', () => { const pathToSearch = ['a', 'b', 'c'] const input = {a: {b: {c: 1}}} const target = {c: 1} const result = pathEq(pathToSearch, input, target) const curriedResult = pathEq(pathToSearch, input, target) result // $ExpectType boolean curriedResult // $ExpectType boolean }) }) describe('with ramda specs', () => { const testPath = ['x', 0, 'y'] const testObj = { x: [ {y: 2, z: 3}, {y: 4, z: 5}, ], } const result1 = pathEq(testPath, 2, testObj) const result2 = pathEq(testPath, 2)(testObj) const result3 = pathEq(testPath)(2)(testObj) result1 // $ExpectType boolean result2 // $ExpectType boolean result3 // $ExpectType boolean }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#pathEq) ### pathOr ```typescript pathOr(defaultValue: T, pathToSearch: Path, obj: any): T ``` It reads `obj` input and returns either `R.path(pathToSearch, Record)` result or `defaultValue` input. Try this R.pathOr example in Rambda REPL

All Typescript definitions

```typescript pathOr(defaultValue: T, pathToSearch: Path, obj: any): T; pathOr(defaultValue: T, pathToSearch: Path): (obj: any) => T; pathOr(defaultValue: T): (pathToSearch: Path) => (obj: any) => T; ```

R.pathOr source

```javascript import { curry } from './curry.js' import { defaultTo } from './defaultTo.js' import { path } from './path.js' function pathOrFn( defaultValue, pathInput, obj ){ return defaultTo(defaultValue, path(pathInput, obj)) } export const pathOr = curry(pathOrFn) ```

Tests

```javascript import { pathOr } from './pathOr.js' test('with undefined', () => { const result = pathOr( 'foo', 'x.y', { x : { y : 1 } } ) expect(result).toBe(1) }) test('with null', () => { const result = pathOr( 'foo', 'x.y', null ) expect(result).toBe('foo') }) test('with NaN', () => { const result = pathOr( 'foo', 'x.y', NaN ) expect(result).toBe('foo') }) test('curry case (x)(y)(z)', () => { const result = pathOr('foo')('x.y.z')({ x : { y : { a : 1 } } }) expect(result).toBe('foo') }) test('curry case (x)(y,z)', () => { const result = pathOr('foo', 'x.y.z')({ x : { y : { a : 1 } } }) expect(result).toBe('foo') }) test('curry case (x,y)(z)', () => { const result = pathOr('foo')('x.y.z', { x : { y : { a : 1 } } }) expect(result).toBe('foo') }) ```

Typescript test

```typescript import {pathOr} from 'rambda' describe('R.pathOr', () => { it('with string path', () => { const x = pathOr('foo', 'x.y', {x: {y: 'bar'}}) x // $ExpectType string }) it('with array path', () => { const x = pathOr('foo', ['x', 'y'], {x: {y: 'bar'}}) x // $ExpectType string }) it('without passing type looks bad', () => { const x = pathOr('foo', 'x.y', {x: {y: 'bar'}}) x // $ExpectType "foo" }) it('curried', () => { const x = pathOr('foo', 'x.y')({x: {y: 'bar'}}) x // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#pathOr) ### paths ```typescript paths(pathsToSearch: Path[], obj: Input): (T | undefined)[] ``` It loops over members of `pathsToSearch` as `singlePath` and returns the array produced by `R.path(singlePath, Record)`. Because it calls `R.path`, then `singlePath` can be either string or a list. Try this R.paths example in Rambda REPL

All Typescript definitions

```typescript paths(pathsToSearch: Path[], obj: Input): (T | undefined)[]; paths(pathsToSearch: Path[]): (obj: Input) => (T | undefined)[]; paths(pathsToSearch: Path[], obj: any): (T | undefined)[]; paths(pathsToSearch: Path[]): (obj: any) => (T | undefined)[]; ```

R.paths source

```javascript import { path } from './path.js' export function paths(pathsToSearch, obj){ if (arguments.length === 1){ return _obj => paths(pathsToSearch, _obj) } return pathsToSearch.map(singlePath => path(singlePath, obj)) } ```

Tests

```javascript import { paths } from './paths.js' const obj = { a : { b : { c : 1, d : 2, }, }, p : [ { q : 3 } ], x : { y : 'FOO', z : [ [ {} ] ], }, } test('with string path + curry', () => { const pathsInput = [ 'a.b.d', 'p.q' ] const expected = [ 2, undefined ] const result = paths(pathsInput, obj) const curriedResult = paths(pathsInput)(obj) expect(result).toEqual(expected) expect(curriedResult).toEqual(expected) }) test('with array path', () => { const result = paths([ [ 'a', 'b', 'c' ], [ 'x', 'y' ], ], obj) expect(result).toEqual([ 1, 'FOO' ]) }) test('takes a paths that contains indices into arrays', () => { expect(paths([ [ 'p', 0, 'q' ], [ 'x', 'z', 0, 0 ], ], obj)).toEqual([ 3, {} ]) expect(paths([ [ 'p', 0, 'q' ], [ 'x', 'z', 2, 1 ], ], obj)).toEqual([ 3, undefined ]) }) test('gets a deep property\'s value from objects', () => { expect(paths([ [ 'a', 'b' ] ], obj)).toEqual([ obj.a.b ]) expect(paths([ [ 'p', 0 ] ], obj)).toEqual([ obj.p[ 0 ] ]) }) test('returns undefined for items not found', () => { expect(paths([ [ 'a', 'x', 'y' ] ], obj)).toEqual([ undefined ]) expect(paths([ [ 'p', 2 ] ], obj)).toEqual([ undefined ]) }) ```

Typescript test

```typescript import {paths} from 'rambda' interface Input { a: number, b: number, c: number, } const input: Input = {a: 1, b: 2, c: 3} describe('R.paths', () => { it('with dot notation', () => { const result = paths(['a.b.c', 'foo.bar'], input) result // $ExpectType (number | undefined)[] }) it('without type', () => { const result = paths(['a.b.c', 'foo.bar'], input) result // $ExpectType unknown[] }) it('with array as path', () => { const result = paths([['a', 'b', 'c'], ['foo.bar']], input) result // $ExpectType (number | undefined)[] }) it('curried', () => { const result = paths([['a', 'b', 'c'], ['foo.bar']])(input) result // $ExpectType (number | undefined)[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#paths) ### pick ```typescript pick(propsToPick: K[], input: T): Pick>> ``` It returns a partial copy of an `input` containing only `propsToPick` properties. `input` can be either an object or an array. String annotation of `propsToPick` is one of the differences between `Rambda` and `Ramda`. Try this R.pick example in Rambda REPL

All Typescript definitions

```typescript pick(propsToPick: K[], input: T): Pick>>; pick(propsToPick: K[]): (input: T) => Pick>>; pick(propsToPick: string, input: T): U; pick(propsToPick: string): (input: T) => U; pick(propsToPick: string, input: object): T; pick(propsToPick: string): (input: object) => T; ```

R.pick source

```javascript import { createPath } from './_internals/createPath.js' export function pick(propsToPick, input){ if (arguments.length === 1) return _input => pick(propsToPick, _input) if (input === null || input === undefined){ return undefined } const keys = createPath(propsToPick, ',') const willReturn = {} let counter = 0 while (counter < keys.length){ if (keys[ counter ] in input){ willReturn[ keys[ counter ] ] = input[ keys[ counter ] ] } counter++ } return willReturn } ```

Tests

```javascript import { pick } from './pick.js' const obj = { a : 1, b : 2, c : 3, } test('props to pick is a string', () => { const result = pick('a,c', obj) const resultCurry = pick('a,c')(obj) const expectedResult = { a : 1, c : 3, } expect(result).toEqual(expectedResult) expect(resultCurry).toEqual(expectedResult) }) test('when prop is missing', () => { const result = pick('a,d,f', obj) expect(result).toEqual({ a : 1 }) }) test('with list indexes as props', () => { const list = [ 1, 2, 3 ] const expected = { 0 : 1, 2 : 3, } expect(pick([ 0, 2, 3 ], list)).toEqual(expected) expect(pick('0,2,3', list)).toEqual(expected) }) test('props to pick is an array', () => { expect(pick([ 'a', 'c' ])({ a : 'foo', b : 'bar', c : 'baz', })).toEqual({ a : 'foo', c : 'baz', }) expect(pick([ 'a', 'd', 'e', 'f' ])({ a : 'foo', b : 'bar', c : 'baz', })).toEqual({ a : 'foo' }) expect(pick('a,d,e,f')(null)).toBeUndefined() }) test('works with list as input and number as props - props to pick is an array', () => { const result = pick([ 1, 2 ], [ 'a', 'b', 'c', 'd' ]) expect(result).toEqual({ 1 : 'b', 2 : 'c', }) }) test('works with list as input and number as props - props to pick is a string', () => { const result = pick('1,2', [ 'a', 'b', 'c', 'd' ]) expect(result).toEqual({ 1 : 'b', 2 : 'c', }) }) test('with symbol', () => { const symbolProp = Symbol('s') expect(pick([ symbolProp ], { [ symbolProp ] : 'a' })).toMatchInlineSnapshot(` { Symbol(s): "a", } `) }) ```

Typescript test

```typescript import {pick} from 'rambda' const input = {a: 'foo', b: 2, c: 3, d: 4} describe('R.pick with array as props input', () => { it('without passing type', () => { const result = pick(['a', 'c'], input) result.a // $ExpectType string result.c // $ExpectType number }) }) describe('R.pick with string as props input', () => { interface Input { a: string, b: number, c: number, d: number, } interface Output { a: string, c: number, } it('explicitly declare output', () => { const result = pick('a,c', input) result // $ExpectType Output result.a // $ExpectType string result.c // $ExpectType number const curriedResult = pick('a,c')(input) curriedResult.a // $ExpectType string }) it('explicitly declare input and output', () => { const result = pick('a,c', input) result // $ExpectType Output result.a // $ExpectType string const curriedResult = pick('a,c')(input) curriedResult.a // $ExpectType string }) it('without passing type', () => { const result = pick('a,c', input) result // $ExpectType unknown }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#pick) ### pickAll ```typescript pickAll(propsToPicks: K[], input: T): Pick ``` Same as `R.pick` but it won't skip the missing props, i.e. it will assign them to `undefined`. Try this R.pickAll example in Rambda REPL

All Typescript definitions

```typescript pickAll(propsToPicks: K[], input: T): Pick; pickAll(propsToPicks: string[], input: T): U; pickAll(propsToPicks: string[]): (input: T) => U; pickAll(propsToPick: string, input: T): U; pickAll(propsToPick: string): (input: T) => U; ```

R.pickAll source

```javascript import { createPath } from './_internals/createPath.js' export function pickAll(propsToPick, obj){ if (arguments.length === 1) return _obj => pickAll(propsToPick, _obj) if (obj === null || obj === undefined){ return undefined } const keysValue = createPath(propsToPick, ',') const willReturn = {} let counter = 0 while (counter < keysValue.length){ if (keysValue[ counter ] in obj){ willReturn[ keysValue[ counter ] ] = obj[ keysValue[ counter ] ] } else { willReturn[ keysValue[ counter ] ] = undefined } counter++ } return willReturn } ```

Tests

```javascript import { pickAll } from './pickAll.js' test('when input is undefined or null', () => { expect(pickAll('a', null)).toBeUndefined() expect(pickAll('a', undefined)).toBeUndefined() }) test('with string as condition', () => { const obj = { a : 1, b : 2, c : 3, } const result = pickAll('a,c', obj) const resultCurry = pickAll('a,c')(obj) const expectedResult = { a : 1, b : undefined, c : 3, } expect(result).toEqual(expectedResult) expect(resultCurry).toEqual(expectedResult) }) test('with array as condition', () => { expect(pickAll([ 'a', 'b', 'c' ], { a : 'foo', c : 'baz', })).toEqual({ a : 'foo', b : undefined, c : 'baz', }) }) ```

Typescript test

```typescript import {pickAll} from 'rambda' interface Input { a: string, b: number, c: number, d: number, } interface Output { a?: string, c?: number, } const input = {a: 'foo', b: 2, c: 3, d: 4} describe('R.pickAll with array as props input', () => { it('without passing type', () => { const result = pickAll(['a', 'c'], input) result.a // $ExpectType string result.c // $ExpectType number }) it('without passing type + curry', () => { const result = pickAll(['a', 'c'])(input) result // $ExpectType unknown }) it('explicitly passing types', () => { const result = pickAll(['a', 'c'], input) result.a // $ExpectType string | undefined result.c // $ExpectType number | undefined }) }) describe('R.pickAll with string as props input', () => { it('without passing type', () => { const result = pickAll('a,c', input) result // $ExpectType unknown }) it('without passing type + curry', () => { const result = pickAll('a,c')(input) result // $ExpectType unknown }) it('explicitly passing types', () => { const result = pickAll('a,c', input) result.a // $ExpectType string | undefined result.c // $ExpectType number | undefined }) it('explicitly passing types + curry', () => { const result = pickAll('a,c')(input) result.a // $ExpectType string | undefined result.c // $ExpectType number | undefined }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#pickAll) ### pipe It performs left-to-right function composition. Try this R.pipe example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#pipe) ### pluck ```typescript pluck(property: K, list: T[]): T[K][] ``` It returns list of the values of `property` taken from the all objects inside `list`. Try this R.pluck example in Rambda REPL

All Typescript definitions

```typescript pluck(property: K, list: T[]): T[K][]; pluck(property: number, list: { [k: number]: T }[]): T[]; pluck

(property: P): (list: Record[]) => T[]; pluck(property: number): (list: { [k: number]: T }[]) => T[]; ```

R.pluck source

```javascript import { map } from './map.js' export function pluck(property, list){ if (arguments.length === 1) return _list => pluck(property, _list) const willReturn = [] map(x => { if (x[ property ] !== undefined){ willReturn.push(x[ property ]) } }, list) return willReturn } ```

Tests

```javascript import { pluck } from './pluck.js' test('happy', () => { expect(pluck('a')([ { a : 1 }, { a : 2 }, { b : 1 } ])).toEqual([ 1, 2 ]) }) test('with number', () => { const input = [ [ 1, 2 ], [ 3, 4 ], ] expect(pluck(0, input)).toEqual([ 1, 3 ]) }) ```

Typescript test

```typescript import {pluck} from 'rambda' describe('R.pluck', () => { it('with object', () => { interface ListMember { a: number, b: string, } const input: ListMember[] = [ {a: 1, b: 'foo'}, {a: 2, b: 'bar'}, ] const resultA = pluck('a', input) const resultB = pluck('b')(input) resultA // $ExpectType number[] resultB // $ExpectType string[] }) it('with array', () => { const input = [ [1, 2], [3, 4], [5, 6], ] const result = pluck(0, input) const resultCurry = pluck(0)(input) result // $ExpectType number[] resultCurry // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#pluck) ### prepend ```typescript prepend(x: T, input: T[]): T[] ``` It adds element `x` at the beginning of `list`. Try this R.prepend example in Rambda REPL

All Typescript definitions

```typescript prepend(x: T, input: T[]): T[]; prepend(x: T): (input: T[]) => T[]; ```

R.prepend source

```javascript export function prepend(x, input){ if (arguments.length === 1) return _input => prepend(x, _input) if (typeof input === 'string') return [ x ].concat(input.split('')) return [ x ].concat(input) } ```

Tests

```javascript import { prepend } from './prepend.js' test('happy', () => { expect(prepend('yes', [ 'foo', 'bar', 'baz' ])).toEqual([ 'yes', 'foo', 'bar', 'baz', ]) }) test('with empty list', () => { expect(prepend('foo')([])).toEqual([ 'foo' ]) }) test('with string instead of array', () => { expect(prepend('foo')('bar')).toEqual([ 'foo', 'b', 'a', 'r' ]) }) ```

Typescript test

```typescript import {prepend} from 'rambda' const list = [1, 2, 3] describe('R.prepend', () => { it('happy', () => { const result = prepend(4, list) result // $ExpectType number[] }) it('curried', () => { const result = prepend(4)(list) result // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#prepend) ### product ```typescript product(list: number[]): number ``` Try this R.product example in Rambda REPL

All Typescript definitions

```typescript product(list: number[]): number; ```

R.product source

```javascript import { multiply } from './multiply.js' import { reduce } from './reduce.js' export const product = reduce(multiply, 1) ```

Tests

```javascript import { product } from './product.js' test('happy', () => { expect(product([ 2, 3, 4 ])).toBe(24) }) test('bad input', () => { expect(product([ null ])).toBe(0) expect(product([])).toBe(1) }) ```

Typescript test

```typescript import {product} from 'rambda' describe('R.product', () => { it('happy', () => { const result = product([1, 2, 3]) result // $ExpectType number }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#product) ### prop ```typescript prop

(propToFind: P, value: T): Prop ``` It returns the value of property `propToFind` in `obj`. If there is no such property, it returns `undefined`. Try this R.prop example in Rambda REPL

All Typescript definitions

```typescript prop

(propToFind: P, value: T): Prop; prop

(propToFind: P): { (value: Record): T; (value: T): Prop; }; prop

(propToFind: P): { (value: T): Prop; }; prop

(propToFind: P): { (value: Record): T; }; ```

R.prop source

```javascript export function prop(propToFind, obj){ if (arguments.length === 1) return _obj => prop(propToFind, _obj) if (!obj) return undefined return obj[ propToFind ] } ```

Tests

```javascript import { prop } from './prop.js' test('prop', () => { expect(prop('foo')({ foo : 'baz' })).toBe('baz') expect(prop('bar')({ foo : 'baz' })).toBeUndefined() expect(prop('bar')(null)).toBeUndefined() }) ```

Typescript test

```typescript import {pipe, prop} from 'rambda' describe('R.prop', () => { const obj = {a: 1, b: 'foo'} interface Something { a?: number, b?: string, } it('issue #553', () => { const result = prop('e', {e: 'test1', d: 'test2'}) const curriedResult = prop('e')({e: 'test1', d: 'test2'}) result // $ExpectType string curriedResult // $ExpectType string }) it('happy', () => { const result = prop('a', obj) result // $ExpectType number }) it('curried', () => { const result = prop('b')(obj) result // $ExpectType string }) it('curried with explicit object type', () => { const result = prop<'a', Something>('a')(obj) result // $ExpectType number | undefined }) it('curried with implicit object type', () => { const result = pipe(value => value as Something, prop('b'))(obj) result // $ExpectType undefined }) it('curried with explicit result type', () => { const result = prop<'b', string>('b')(obj) result // $ExpectType string }) }) describe('with number as prop', () => { const list = [1, 2, 3] const index = 1 it('happy', () => { const result = prop(index, list) result // $ExpectType number }) it('curried require explicit type', () => { const result = prop(index)(list) result // $ExpectType number }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#prop) ### propEq ```typescript propEq(propToFind: K, valueToMatch: any, obj: Record): boolean ``` It returns true if `obj` has property `propToFind` and its value is equal to `valueToMatch`. Try this R.propEq example in Rambda REPL

All Typescript definitions

```typescript propEq(propToFind: K, valueToMatch: any, obj: Record): boolean; propEq(propToFind: K, valueToMatch: any): (obj: Record) => boolean; propEq(propToFind: K): { (valueToMatch: any, obj: Record): boolean; (valueToMatch: any): (obj: Record) => boolean; }; ```

R.propEq source

```javascript import { curry } from './curry.js' import { equals } from './equals.js' import { prop } from './prop.js' function propEqFn( propToFind, valueToMatch, obj ){ if (!obj) return false return equals(valueToMatch, prop(propToFind, obj)) } export const propEq = curry(propEqFn) ```

Tests

```javascript import { propEq } from './propEq.js' test('happy', () => { expect(propEq('foo', 'bar')({ foo : 'bar' })).toBeTrue() expect(propEq('foo', 'bar')({ foo : 'baz' })).toBeFalse() expect(propEq('foo')('bar')({ foo : 'baz' })).toBeFalse() expect(propEq( 'foo', 'bar', null )).toBeFalse() }) test('returns false if called with a null or undefined object', () => { expect(propEq( 'name', 'Abby', null )).toBeFalse() expect(propEq( 'name', 'Abby', undefined )).toBeFalse() }) ```

Typescript test

```typescript import {propEq} from 'rambda' const property = 'foo' const numberProperty = 1 const value = 'bar' const obj = {[property]: value} const objWithNumberIndex = {[numberProperty]: value} describe('R.propEq', () => { it('happy', () => { const result = propEq(property, value, obj) result // $ExpectType boolean }) it('number is property', () => { const result = propEq(1, value, objWithNumberIndex) result // $ExpectType boolean }) it('with optional property', () => { interface MyType { optional?: string | number, } const myObject: MyType = {} const valueToFind = '1111' // @ts-expect-error propEq('optional', valueToFind, myObject) // @ts-expect-error propEq('optional', valueToFind, myObject) }) it('imported from @types/ramda', () => { interface A { foo: string | null, } const obj: A = { foo: 'bar', } const value = '' const result = propEq('foo', value)(obj) result // $ExpectType boolean // @ts-expect-error propEq('bar', value)(obj) }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#propEq) ### propIs ```typescript propIs(type: C, name: K, obj: any): obj is Record> ``` It returns `true` if `property` of `obj` is from `target` type. Try this R.propIs example in Rambda REPL

All Typescript definitions

```typescript propIs(type: C, name: K, obj: any): obj is Record>; propIs(type: C, name: K, obj: any): obj is Record>; propIs(type: C, name: K): (obj: any) => obj is Record>; propIs(type: C, name: K): (obj: any) => obj is Record>; propIs(type: C): { (name: K, obj: any): obj is Record>; (name: K): (obj: any) => obj is Record>; }; ```

R.propIs source

```javascript import { curry } from './curry.js' import { is } from './is.js' function propIsFn( targetPrototype, property, obj ){ return is(targetPrototype, obj[ property ]) } export const propIs = curry(propIsFn) ```

Tests

```javascript import { propIs } from './propIs.js' const obj = { a : 1, b : 'foo', } test('when true', () => { expect(propIs( Number, 'a', obj )).toBeTrue() expect(propIs( String, 'b', obj )).toBeTrue() }) test('when false', () => { expect(propIs( String, 'a', obj )).toBeFalse() expect(propIs( Number, 'b', obj )).toBeFalse() }) ```

Typescript test

```typescript import {propIs} from 'rambda' const property = 'a' const obj = {a: 1} describe('R.propIs', () => { it('happy', () => { const result = propIs(Number, property, obj) result // $ExpectType boolean }) it('curried', () => { const result = propIs(Number, property)(obj) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#propIs) ### propOr ```typescript propOr(defaultValue: T, property: P, obj: Partial> | undefined): T ``` It returns either `defaultValue` or the value of `property` in `obj`. Try this R.propOr example in Rambda REPL

All Typescript definitions

```typescript propOr(defaultValue: T, property: P, obj: Partial> | undefined): T; propOr(defaultValue: T, property: P): (obj: Partial> | undefined) => T; propOr(defaultValue: T): {

(property: P, obj: Partial> | undefined): T;

(property: P): (obj: Partial> | undefined) => T; } ```

R.propOr source

```javascript import { curry } from './curry.js' import { defaultTo } from './defaultTo.js' function propOrFn( defaultValue, property, obj ){ if (!obj) return defaultValue return defaultTo(defaultValue, obj[ property ]) } export const propOr = curry(propOrFn) ```

Tests

```javascript import { propOr } from './propOr.js' test('propOr (result)', () => { const obj = { a : 1 } expect(propOr( 'default', 'a', obj )).toBe(1) expect(propOr( 'default', 'notExist', obj )).toBe('default') expect(propOr( 'default', 'notExist', null )).toBe('default') }) test('propOr (currying)', () => { const obj = { a : 1 } expect(propOr('default')('a', obj)).toBe(1) expect(propOr('default', 'a')(obj)).toBe(1) expect(propOr('default')('notExist', obj)).toBe('default') expect(propOr('default', 'notExist')(obj)).toBe('default') }) ```

Typescript test

```typescript import {propOr} from 'rambda' const obj = {foo: 'bar'} const property = 'foo' const fallback = 'fallback' describe('R.propOr', () => { it('happy', () => { const result = propOr(fallback, property, obj) result // $ExpectType string }) it('curry 1', () => { const result = propOr(fallback)(property, obj) result // $ExpectType string }) it('curry 2', () => { const result = propOr(fallback, property)(obj) result // $ExpectType string }) it('curry 3', () => { const result = propOr(fallback)(property)(obj) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#propOr) ### props ```typescript props

(propsToPick: P[], obj: Record): T[] ``` It takes list with properties `propsToPick` and returns a list with property values in `obj`. Try this R.props example in Rambda REPL

All Typescript definitions

```typescript props

(propsToPick: P[], obj: Record): T[]; props

(propsToPick: P[]): (obj: Record) => T[]; props

(propsToPick: P[]): (obj: Record) => T[]; ```

R.props source

```javascript import { isArray } from './_internals/isArray.js' import { mapArray } from './map.js' export function props(propsToPick, obj){ if (arguments.length === 1){ return _obj => props(propsToPick, _obj) } if (!isArray(propsToPick)){ throw new Error('propsToPick is not a list') } return mapArray(prop => obj[ prop ], propsToPick) } ```

Tests

```javascript import { props } from './props.js' const obj = { a : 1, b : 2, } const propsToPick = [ 'a', 'c' ] test('happy', () => { const result = props(propsToPick, obj) expect(result).toEqual([ 1, undefined ]) }) test('curried', () => { const result = props(propsToPick)(obj) expect(result).toEqual([ 1, undefined ]) }) test('wrong input', () => { expect(() => props(null)(obj)).toThrowErrorMatchingInlineSnapshot('"propsToPick is not a list"') }) ```

Typescript test

```typescript import {props} from 'rambda' const obj = {a: 1, b: 2} describe('R.props', () => { it('happy', () => { const result = props(['a', 'b'], obj) result // $ExpectType number[] }) it('curried', () => { const result = props(['a', 'b'])(obj) result // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#props) ### propSatisfies ```typescript propSatisfies(predicate: Predicate, property: string, obj: Record): boolean ``` It returns `true` if the object property satisfies a given predicate. Try this R.propSatisfies example in Rambda REPL

All Typescript definitions

```typescript propSatisfies(predicate: Predicate, property: string, obj: Record): boolean; propSatisfies(predicate: Predicate, property: string): (obj: Record) => boolean; ```

R.propSatisfies source

```javascript import { curry } from './curry.js' import { prop } from './prop.js' function propSatisfiesFn( predicate, property, obj ){ return predicate(prop(property, obj)) } export const propSatisfies = curry(propSatisfiesFn) ```

Tests

```javascript import { propSatisfies } from './propSatisfies.js' const obj = { a : 1 } test('when true', () => { expect(propSatisfies( x => x > 0, 'a', obj )).toBeTrue() }) test('when false', () => { expect(propSatisfies(x => x < 0, 'a')(obj)).toBeFalse() }) ```

Typescript test

```typescript import {propSatisfies} from 'rambda' const obj = {a: 1} describe('R.propSatisfies', () => { it('happy', () => { const result = propSatisfies(x => x > 0, 'a', obj) result // $ExpectType boolean }) it('curried requires explicit type', () => { const result = propSatisfies(x => x > 0, 'a')(obj) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#propSatisfies) ### range ```typescript range(startInclusive: number, endExclusive: number): number[] ``` It returns list of numbers between `startInclusive` to `endExclusive` markers. Try this R.range example in Rambda REPL

All Typescript definitions

```typescript range(startInclusive: number, endExclusive: number): number[]; range(startInclusive: number): (endExclusive: number) => number[]; ```

R.range source

```javascript export function range(start, end){ if (arguments.length === 1) return _end => range(start, _end) if (Number.isNaN(Number(start)) || Number.isNaN(Number(end))){ throw new TypeError('Both arguments to range must be numbers') } if (end < start) return [] const len = end - start const willReturn = Array(len) for (let i = 0; i < len; i++){ willReturn[ i ] = start + i } return willReturn } ```

Tests

```javascript import { range } from './range.js' test('happy', () => { expect(range(0, 10)).toEqual([ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]) }) test('end range is bigger than start range', () => { expect(range(7, 3)).toEqual([]) expect(range(5, 5)).toEqual([]) }) test('with bad input', () => { const throwMessage = 'Both arguments to range must be numbers' expect(() => range('a', 6)).toThrowWithMessage(Error, throwMessage) expect(() => range(6, 'z')).toThrowWithMessage(Error, throwMessage) }) test('curry', () => { expect(range(0)(10)).toEqual([ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]) }) ```

Typescript test

```typescript import {range} from 'rambda' describe('R.range', () => { it('happy', () => { const result = range(1, 4) result // $ExpectType number[] }) it('curried', () => { const result = range(1)(4) result // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#range) ### reduce Try this R.reduce example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#reduce) ### reject ```typescript reject(predicate: Predicate, list: T[]): T[] ``` It has the opposite effect of `R.filter`. Try this R.reject example in Rambda REPL

All Typescript definitions

```typescript reject(predicate: Predicate, list: T[]): T[]; reject(predicate: Predicate): (list: T[]) => T[]; reject(predicate: Predicate, obj: Dictionary): Dictionary; reject(predicate: Predicate): (obj: Dictionary) => Dictionary; ```

R.reject source

```javascript import { filter } from './filter.js' export function reject(predicate, list){ if (arguments.length === 1) return _list => reject(predicate, _list) return filter(x => !predicate(x), list) } ```

Tests

```javascript import { reject } from './reject.js' const isOdd = n => n % 2 === 1 test('with array', () => { expect(reject(isOdd)([ 1, 2, 3, 4 ])).toEqual([ 2, 4 ]) }) test('with object', () => { const obj = { a : 1, b : 2, c : 3, d : 4, } expect(reject(isOdd, obj)).toEqual({ b : 2, d : 4, }) }) ```

Typescript test

```typescript import {reject} from 'rambda' describe('R.reject with array', () => { it('happy', () => { const result = reject( x => { x // $ExpectType number return x > 1 }, [1, 2, 3] ) result // $ExpectType number[] }) it('curried require explicit type', () => { const result = reject(x => { x // $ExpectType number return x > 1 })([1, 2, 3]) result // $ExpectType number[] }) }) describe('R.reject with objects', () => { it('happy', () => { const result = reject( x => { x // $ExpectType number return x > 1 }, {a: 1, b: 2} ) result // $ExpectType Dictionary }) it('curried require dummy type', () => { const result = reject(x => { return x > 1 })({a: 1, b: 2}) result // $ExpectType Dictionary }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#reject) ### repeat ```typescript repeat(x: T): (timesToRepeat: number) => T[] ``` Try this R.repeat example in Rambda REPL

All Typescript definitions

```typescript repeat(x: T): (timesToRepeat: number) => T[]; repeat(x: T, timesToRepeat: number): T[]; ```

R.repeat source

```javascript export function repeat(x, timesToRepeat){ if (arguments.length === 1){ return _timesToRepeat => repeat(x, _timesToRepeat) } return Array(timesToRepeat).fill(x) } ```

Tests

```javascript import { repeat } from './repeat.js' test('repeat', () => { expect(repeat('')(3)).toEqual([ '', '', '' ]) expect(repeat('foo', 3)).toEqual([ 'foo', 'foo', 'foo' ]) const obj = {} const arr = repeat(obj, 3) expect(arr).toEqual([ {}, {}, {} ]) expect(arr[ 0 ] === arr[ 1 ]).toBeTrue() }) ```

Typescript test

```typescript import {repeat} from 'rambda' describe('R.repeat', () => { it('happy', () => { const result = repeat(4, 7) result // $ExpectType number[] }) it('curried', () => { const result = repeat(4)(7) result // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#repeat) ### replace ```typescript replace(strOrRegex: RegExp | string, replacer: string, str: string): string ``` It replaces `strOrRegex` found in `str` with `replacer`. Try this R.replace example in Rambda REPL

All Typescript definitions

```typescript replace(strOrRegex: RegExp | string, replacer: string, str: string): string; replace(strOrRegex: RegExp | string, replacer: string): (str: string) => string; replace(strOrRegex: RegExp | string): (replacer: string) => (str: string) => string; ```

R.replace source

```javascript import { curry } from './curry.js' function replaceFn( pattern, replacer, str ){ return str.replace(pattern, replacer) } export const replace = curry(replaceFn) ```

Tests

```javascript import { replace } from './replace.js' test('happy', () => { expect(replace( 'foo', 'yes', 'foo bar baz' )).toBe('yes bar baz') }) test('1', () => { expect(replace(/\s/g)('|')('foo bar baz')).toBe('foo|bar|baz') }) test('2', () => { expect(replace(/\s/g)('|', 'foo bar baz')).toBe('foo|bar|baz') }) test('3', () => { expect(replace(/\s/g, '|')('foo bar baz')).toBe('foo|bar|baz') }) ```

Typescript test

```typescript import {replace} from 'rambda' const str = 'foo bar foo' const replacer = 'bar' describe('R.replace', () => { it('happy', () => { const result = replace(/foo/g, replacer, str) result // $ExpectType string }) it('with string as search pattern', () => { const result = replace('foo', replacer, str) result // $ExpectType string }) }) describe('R.replace - curried', () => { it('happy', () => { const result = replace(/foo/g, replacer)(str) result // $ExpectType string }) it('with string as search pattern', () => { const result = replace('foo', replacer)(str) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#replace) ### reverse ```typescript reverse(input: T[]): T[] ``` It returns a reversed copy of list or string `input`. Try this R.reverse example in Rambda REPL

All Typescript definitions

```typescript reverse(input: T[]): T[]; reverse(input: string): string; ```

R.reverse source

```javascript export function reverse(listOrString){ if (typeof listOrString === 'string'){ return listOrString.split('').reverse() .join('') } const clone = listOrString.slice() return clone.reverse() } ```

Tests

```javascript import { reverse } from './reverse.js' test('happy', () => { expect(reverse([ 1, 2, 3 ])).toEqual([ 3, 2, 1 ]) }) test('with string', () => { expect(reverse('baz')).toBe('zab') }) test('it doesn\'t mutate', () => { const arr = [ 1, 2, 3 ] expect(reverse(arr)).toEqual([ 3, 2, 1 ]) expect(arr).toEqual([ 1, 2, 3 ]) }) ```

Typescript test

```typescript import {reverse} from 'rambda' const list = [1, 2, 3, 4, 5] describe('R.reverse', () => { it('happy', () => { const result = reverse(list) result // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#reverse) ### set ```typescript set(lens: Lens, replacer: U, obj: T): T ``` It returns a copied **Object** or **Array** with modified `lens` focus set to `replacer` value. Try this R.set example in Rambda REPL

All Typescript definitions

```typescript set(lens: Lens, replacer: U, obj: T): T; set(lens: Lens, replacer: U): (obj: T) => T; set(lens: Lens): (replacer: U, obj: T) => T; ```

R.set source

```javascript import { always } from './always.js' import { curry } from './curry.js' import { over } from './over.js' function setFn( lens, replacer, x ){ return over( lens, always(replacer), x ) } export const set = curry(setFn) ```

Tests

```javascript import { assoc } from './assoc.js' import { lens } from './lens.js' import { lensIndex } from './lensIndex.js' import { lensPath } from './lensPath.js' import { prop } from './prop.js' import { set } from './set.js' const testObject = { foo : 'bar', baz : { a : 'x', b : 'y', }, } test('assoc lens', () => { const assocLens = lens(prop('foo'), assoc('foo')) const result = set( assocLens, 'FOO', testObject ) const expected = { ...testObject, foo : 'FOO', } expect(result).toEqual(expected) }) test('path lens', () => { const pathLens = lensPath('baz.a') const result = set( pathLens, 'z', testObject ) const expected = { ...testObject, baz : { a : 'z', b : 'y', }, } expect(result).toEqual(expected) }) test('index lens', () => { const indexLens = lensIndex(0) const result = set( indexLens, 3, [ 1, 2 ] ) expect(result).toEqual([ 3, 2 ]) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#set) ### slice ```typescript slice(from: number, to: number, input: string): string ``` Try this R.slice example in Rambda REPL

All Typescript definitions

```typescript slice(from: number, to: number, input: string): string; slice(from: number, to: number, input: T[]): T[]; slice(from: number, to: number): { (input: string): string; (input: T[]): T[]; }; slice(from: number): { (to: number, input: string): string; (to: number, input: T[]): T[]; }; ```

R.slice source

```javascript import { curry } from './curry.js' function sliceFn( from, to, list ){ return list.slice(from, to) } export const slice = curry(sliceFn) ```

Tests

```javascript import { slice } from './slice.js' test('slice', () => { expect(slice( 1, 3, [ 'a', 'b', 'c', 'd' ] )).toEqual([ 'b', 'c' ]) expect(slice( 1, Infinity, [ 'a', 'b', 'c', 'd' ] )).toEqual([ 'b', 'c', 'd' ]) expect(slice( 0, -1, [ 'a', 'b', 'c', 'd' ] )).toEqual([ 'a', 'b', 'c' ]) expect(slice( -3, -1, [ 'a', 'b', 'c', 'd' ] )).toEqual([ 'b', 'c' ]) expect(slice( 0, 3, 'ramda' )).toBe('ram') }) ```

Typescript test

```typescript import {slice} from 'rambda' const list = [1, 2, 3, 4, 5] describe('R.slice', () => { it('happy', () => { const result = slice(1, 3, list) result // $ExpectType number[] }) it('curried', () => { const result = slice(1, 3)(list) result // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#slice) ### sort ```typescript sort(sortFn: (a: T, b: T) => number, list: T[]): T[] ``` It returns copy of `list` sorted by `sortFn` function, where `sortFn` needs to return only `-1`, `0` or `1`. Try this R.sort example in Rambda REPL

All Typescript definitions

```typescript sort(sortFn: (a: T, b: T) => number, list: T[]): T[]; sort(sortFn: (a: T, b: T) => number): (list: T[]) => T[]; ```

R.sort source

```javascript import { cloneList } from './_internals/cloneList.js' export function sort(sortFn, list){ if (arguments.length === 1) return _list => sort(sortFn, _list) return cloneList(list).sort(sortFn) } ```

Tests

```javascript import { sort } from './sort.js' const fn = (a, b) => a > b ? 1 : -1 test('sort', () => { expect(sort((a, b) => a - b)([ 2, 3, 1 ])).toEqual([ 1, 2, 3 ]) }) test('it doesn\'t mutate', () => { const list = [ 'foo', 'bar', 'baz' ] expect(sort(fn, list)).toEqual([ 'bar', 'baz', 'foo' ]) expect(list[ 0 ]).toBe('foo') expect(list[ 1 ]).toBe('bar') expect(list[ 2 ]).toBe('baz') }) ```

Typescript test

```typescript import {sort} from 'rambda' const list = [3, 0, 5, 2, 1] function sortFn(a: number, b: number): number { return a > b ? 1 : -1 } describe('R.sort', () => { it('happy', () => { const result = sort(sortFn, list) result // $ExpectType number[] }) it('curried', () => { const result = sort(sortFn)(list) result // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#sort) ### sortBy ```typescript sortBy(sortFn: (a: T) => Ord, list: T[]): T[] ``` It returns copy of `list` sorted by `sortFn` function, where `sortFn` function returns a value to compare, i.e. it doesn't need to return only `-1`, `0` or `1`. Try this R.sortBy example in Rambda REPL

All Typescript definitions

```typescript sortBy(sortFn: (a: T) => Ord, list: T[]): T[]; sortBy(sortFn: (a: T) => Ord): (list: T[]) => T[]; sortBy(sortFn: (a: any) => Ord): (list: T[]) => T[]; ```

R.sortBy source

```javascript import { cloneList } from './_internals/cloneList.js' export function sortBy(sortFn, list){ if (arguments.length === 1) return _list => sortBy(sortFn, _list) const clone = cloneList(list) return clone.sort((a, b) => { const aSortResult = sortFn(a) const bSortResult = sortFn(b) if (aSortResult === bSortResult) return 0 return aSortResult < bSortResult ? -1 : 1 }) } ```

Tests

```javascript import { compose } from './compose.js' import { prop } from './prop.js' import { sortBy } from './sortBy.js' import { toLower } from './toLower.js' test('happy', () => { const input = [ { a : 2 }, { a : 1 }, { a : 1 }, { a : 3 } ] const expected = [ { a : 1 }, { a : 1 }, { a : 2 }, { a : 3 } ] const result = sortBy(x => x.a)(input) expect(result).toEqual(expected) }) test('with compose', () => { const alice = { name : 'ALICE', age : 101, } const bob = { name : 'Bob', age : -10, } const clara = { name : 'clara', age : 314.159, } const people = [ clara, bob, alice ] const sortByNameCaseInsensitive = sortBy(compose(toLower, prop('name'))) expect(sortByNameCaseInsensitive(people)).toEqual([ alice, bob, clara ]) }) ```

Typescript test

```typescript import {sortBy, pipe} from 'rambda' interface Input { a: number, } describe('R.sortBy', () => { it('passing type to sort function', () => { function fn(x: any): number { return x.a } function fn2(x: Input): number { return x.a } const input = [{a: 2}, {a: 1}, {a: 0}] const result = sortBy(fn, input) const curriedResult = sortBy(fn2)(input) result // $ExpectType { a: number; }[] curriedResult // $ExpectType Input[] result[0].a // $ExpectType number curriedResult[0].a // $ExpectType number }) it('passing type to sort function and list', () => { function fn(x: Input): number { return x.a } const input: Input[] = [{a: 2}, {a: 1}, {a: 0}] const result = sortBy(fn, input) const curriedResult = sortBy(fn)(input) result // $ExpectType Input[] curriedResult // $ExpectType Input[] result[0].a // $ExpectType number }) it('with R.pipe', () => { interface Obj { value: number, } const fn = pipe(sortBy(x => x.value)) const result = fn([{value: 1}, {value: 2}]) result // $ExpectType Obj[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#sortBy) ### split ```typescript split(separator: string | RegExp): (str: string) => string[] ``` Curried version of `String.prototype.split` Try this R.split example in Rambda REPL

All Typescript definitions

```typescript split(separator: string | RegExp): (str: string) => string[]; split(separator: string | RegExp, str: string): string[]; ```

R.split source

```javascript export function split(separator, str){ if (arguments.length === 1) return _str => split(separator, _str) return str.split(separator) } ```

Tests

```javascript import { split } from './split.js' const str = 'foo|bar|baz' const splitChar = '|' const expected = [ 'foo', 'bar', 'baz' ] test('happy', () => { expect(split(splitChar, str)).toEqual(expected) }) test('curried', () => { expect(split(splitChar)(str)).toEqual(expected) }) ```

Typescript test

```typescript import {split} from 'rambda' const str = 'foo|bar|baz' const splitChar = '|' describe('R.split', () => { it('happy', () => { const result = split(splitChar, str) result // $ExpectType string[] }) it('curried', () => { const result = split(splitChar)(str) result // $ExpectType string[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#split) ### splitAt ```typescript splitAt(index: number, input: T[]): [T[], T[]] ``` It splits string or array at a given index. Try this R.splitAt example in Rambda REPL

All Typescript definitions

```typescript splitAt(index: number, input: T[]): [T[], T[]]; splitAt(index: number, input: string): [string, string]; splitAt(index: number): { (input: T[]): [T[], T[]]; (input: string): [string, string]; }; ```

R.splitAt source

```javascript import { isArray } from './_internals/isArray.js' import { drop } from './drop.js' import { maybe } from './maybe.js' import { take } from './take.js' export function splitAt(index, input){ if (arguments.length === 1){ return _list => splitAt(index, _list) } if (!input) throw new TypeError(`Cannot read property 'slice' of ${ input }`) if (!isArray(input) && typeof input !== 'string') return [ [], [] ] const correctIndex = maybe( index < 0, input.length + index < 0 ? 0 : input.length + index, index ) return [ take(correctIndex, input), drop(correctIndex, input) ] } ```

Tests

```javascript import { splitAt as splitAtRamda } from 'ramda' import { splitAt } from './splitAt.js' const list = [ 1, 2, 3 ] const str = 'foo bar' test('with array', () => { const result = splitAt(2, list) expect(result).toEqual([ [ 1, 2 ], [ 3 ] ]) }) test('with array - index is negative number', () => { const result = splitAt(-6, list) expect(result).toEqual([ [], list ]) }) test('with array - index is out of scope', () => { const result = splitAt(4, list) expect(result).toEqual([ [ 1, 2, 3 ], [] ]) }) test('with string', () => { const result = splitAt(4, str) expect(result).toEqual([ 'foo ', 'bar' ]) }) test('with string - index is negative number', () => { const result = splitAt(-2, str) expect(result).toEqual([ 'foo b', 'ar' ]) }) test('with string - index is out of scope', () => { const result = splitAt(10, str) expect(result).toEqual([ str, '' ]) }) test('with array - index is out of scope', () => { const result = splitAt(4)(list) expect(result).toEqual([ [ 1, 2, 3 ], [] ]) }) const badInputs = [ 1, true, /foo/g, {} ] const throwingBadInputs = [ null, undefined ] test('with bad inputs', () => { throwingBadInputs.forEach(badInput => { expect(() => splitAt(1, badInput)).toThrowWithMessage(TypeError, `Cannot read property 'slice' of ${ badInput }`) expect(() => splitAtRamda(1, badInput)).toThrowWithMessage(TypeError, `Cannot read properties of ${ badInput } (reading 'slice')`) }) badInputs.forEach(badInput => { const result = splitAt(1, badInput) const ramdaResult = splitAtRamda(1, badInput) expect(result).toEqual(ramdaResult) }) }) ```

Typescript test

```typescript import {splitAt} from 'rambda' const index = 1 const str = 'foo' const list = [1, 2, 3] describe('R.splitAt with array', () => { it('happy', () => { const result = splitAt(index, list) result // $ExpectType [number[], number[]] }) it('curried', () => { const result = splitAt(index)(list) result // $ExpectType [number[], number[]] }) }) describe('R.splitAt with string', () => { it('happy', () => { const result = splitAt(index, str) result // $ExpectType [string, string] }) it('curried', () => { const result = splitAt(index)(str) result // $ExpectType [string, string] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#splitAt) ### splitEvery ```typescript splitEvery(sliceLength: number, input: T[]): (T[])[] ``` It splits `input` into slices of `sliceLength`. Try this R.splitEvery example in Rambda REPL

All Typescript definitions

```typescript splitEvery(sliceLength: number, input: T[]): (T[])[]; splitEvery(sliceLength: number, input: string): string[]; splitEvery(sliceLength: number): { (input: string): string[]; (input: T[]): (T[])[]; }; ```

R.splitEvery source

```javascript export function splitEvery(sliceLength, listOrString){ if (arguments.length === 1){ return _listOrString => splitEvery(sliceLength, _listOrString) } if (sliceLength < 1){ throw new Error('First argument to splitEvery must be a positive integer') } const willReturn = [] let counter = 0 while (counter < listOrString.length){ willReturn.push(listOrString.slice(counter, counter += sliceLength)) } return willReturn } ```

Tests

```javascript import { splitEvery } from './splitEvery.js' test('happy', () => { expect(splitEvery(3, [ 1, 2, 3, 4, 5, 6, 7 ])).toEqual([ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7 ], ]) expect(splitEvery(3)('foobarbaz')).toEqual([ 'foo', 'bar', 'baz' ]) }) test('with bad input', () => { expect(() => expect(splitEvery(0)('foo')).toEqual([ 'f', 'o', 'o' ])).toThrowErrorMatchingInlineSnapshot('"First argument to splitEvery must be a positive integer"') }) ```

Typescript test

```typescript import {splitEvery} from 'rambda' const list = [1, 2, 3, 4, 5, 6, 7] describe('R.splitEvery', () => { it('happy', () => { const result = splitEvery(3, list) result // $ExpectType number[][] }) it('curried', () => { const result = splitEvery(3)(list) result // $ExpectType number[][] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#splitEvery) ### splitWhen ```typescript splitWhen(predicate: Predicate, list: U[]): (U[])[] ``` It splits `list` to two arrays according to a `predicate` function. The first array contains all members of `list` before `predicate` returns `true`. Try this R.splitWhen example in Rambda REPL

All Typescript definitions

```typescript splitWhen(predicate: Predicate, list: U[]): (U[])[]; splitWhen(predicate: Predicate): (list: U[]) => (U[])[]; ```

R.splitWhen source

```javascript export function splitWhen(predicate, input){ if (arguments.length === 1){ return _input => splitWhen(predicate, _input) } if (!input) throw new TypeError(`Cannot read property 'length' of ${ input }`) const preFound = [] const postFound = [] let found = false let counter = -1 while (counter++ < input.length - 1){ if (found){ postFound.push(input[ counter ]) } else if (predicate(input[ counter ])){ postFound.push(input[ counter ]) found = true } else { preFound.push(input[ counter ]) } } return [ preFound, postFound ] } ```

Tests

```javascript import { splitWhen as splitWhenRamda } from 'ramda' import { equals } from './equals.js' import { splitWhen } from './splitWhen.js' const list = [ 1, 2, 1, 2 ] test('happy', () => { const result = splitWhen(equals(2), list) expect(result).toEqual([ [ 1 ], [ 2, 1, 2 ] ]) }) test('when predicate returns false', () => { const result = splitWhen(equals(3))(list) expect(result).toEqual([ list, [] ]) }) const badInputs = [ 1, true, /foo/g, {} ] const throwingBadInputs = [ null, undefined ] test('with bad inputs', () => { throwingBadInputs.forEach(badInput => { expect(() => splitWhen(equals(2), badInput)).toThrowWithMessage(TypeError, `Cannot read property 'length' of ${ badInput }`) expect(() => splitWhenRamda(equals(2), badInput)).toThrowWithMessage(TypeError, `Cannot read properties of ${ badInput } (reading 'length')`) }) badInputs.forEach(badInput => { const result = splitWhen(equals(2), badInput) const ramdaResult = splitWhenRamda(equals(2), badInput) expect(result).toEqual(ramdaResult) }) }) ```

Typescript test

```typescript import {splitWhen} from 'rambda' const list = [1, 2, 1, 2] const predicate = (x: number) => x === 2 describe('R.splitWhen', () => { it('happy', () => { const result = splitWhen(predicate, list) result // $ExpectType number[][] }) it('curried', () => { const result = splitWhen(predicate)(list) result // $ExpectType number[][] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#splitWhen) ### startsWith ```typescript startsWith(target: string, str: string): boolean ``` When iterable is a string, then it behaves as `String.prototype.startsWith`. When iterable is a list, then it uses R.equals to determine if the target list starts in the same way as the given target. Try this R.startsWith example in Rambda REPL

All Typescript definitions

```typescript startsWith(target: string, str: string): boolean; startsWith(target: string): (str: string) => boolean; startsWith(target: T[], list: T[]): boolean; startsWith(target: T[]): (list: T[]) => boolean; ```

R.startsWith source

```javascript import { isArray } from './_internals/isArray.js' import { equals } from './equals.js' export function startsWith(target, iterable){ if (arguments.length === 1) return _iterable => startsWith(target, _iterable) if (typeof iterable === 'string'){ return iterable.startsWith(target) } if (!isArray(target)) return false let correct = true const filtered = target.filter((x, index) => { if (!correct) return false const result = equals(x, iterable[ index ]) if (!result) correct = false return result }) return filtered.length === target.length } ```

Tests

```javascript import { startsWith as startsWithRamda } from 'ramda' import { compareCombinations } from './_internals/testUtils.js' import { possibleIterables, possibleTargets } from './endsWith.spec.js' import { startsWith } from './startsWith.js' test('with string', () => { expect(startsWith('foo', 'foo-bar')).toBeTrue() expect(startsWith('baz')('foo-bar')).toBeFalse() }) test('use R.equals with array', () => { const list = [ { a : 1 }, { a : 2 }, { a : 3 } ] expect(startsWith({ a : 1 }, list)).toBeFalse() expect(startsWith([ { a : 1 } ], list)).toBeTrue() expect(startsWith([ { a : 1 }, { a : 2 } ], list)).toBeTrue() expect(startsWith(list, list)).toBeTrue() expect(startsWith([ { a : 2 } ], list)).toBeFalse() }) describe('brute force', () => { compareCombinations({ fn : startsWith, fnRamda : startsWithRamda, firstInput : possibleTargets, secondInput : possibleIterables, callback : errorsCounters => { expect(errorsCounters).toMatchInlineSnapshot(` { "ERRORS_MESSAGE_MISMATCH": 0, "ERRORS_TYPE_MISMATCH": 0, "RESULTS_MISMATCH": 0, "SHOULD_NOT_THROW": 0, "SHOULD_THROW": 0, "TOTAL_TESTS": 32, } `) }, }) }) ```

Typescript test

```typescript import {startsWith} from 'rambda' describe('R.startsWith - array as iterable', () => { const target = [{a: 1}] const iterable = [{a: 1}, {a: 2}] it('happy', () => { const result = startsWith(target, iterable) result // $ExpectType boolean }) it('curried', () => { const result = startsWith(target)(iterable) result // $ExpectType boolean }) }) describe('R.startsWith - string as iterable', () => { const target = 'foo' const iterable = 'foo bar' it('happy', () => { const result = startsWith(target, iterable) result // $ExpectType boolean }) it('curried', () => { const result = startsWith(target)(iterable) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#startsWith) ### subtract Curried version of `x - y` Try this R.subtract example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#subtract) ### sum ```typescript sum(list: number[]): number ``` Try this R.sum example in Rambda REPL

All Typescript definitions

```typescript sum(list: number[]): number; ```

R.sum source

```javascript export function sum(list){ return list.reduce((prev, current) => prev + current, 0) } ```

Tests

```javascript import { sum } from './sum.js' test('happy', () => { expect(sum([ 1, 2, 3, 4, 5 ])).toBe(15) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#sum) ### symmetricDifference ```typescript symmetricDifference(x: T[], y: T[]): T[] ``` It returns a merged list of `x` and `y` with all equal elements removed. `R.equals` is used to determine equality. Try this R.symmetricDifference example in Rambda REPL

All Typescript definitions

```typescript symmetricDifference(x: T[], y: T[]): T[]; symmetricDifference(x: T[]): (y: T[]) => T[]; ```

R.symmetricDifference source

```javascript import { concat } from './concat.js' import { filter } from './filter.js' import { includes } from './includes.js' export function symmetricDifference(x, y){ if (arguments.length === 1){ return _y => symmetricDifference(x, _y) } return concat(filter(value => !includes(value, y), x), filter(value => !includes(value, x), y)) } ```

Tests

```javascript import { symmetricDifference } from './symmetricDifference.js' test('symmetricDifference', () => { const list1 = [ 1, 2, 3, 4 ] const list2 = [ 3, 4, 5, 6 ] expect(symmetricDifference(list1)(list2)).toEqual([ 1, 2, 5, 6 ]) expect(symmetricDifference([], [])).toEqual([]) }) test('symmetricDifference with objects', () => { const list1 = [ { id : 1 }, { id : 2 }, { id : 3 }, { id : 4 } ] const list2 = [ { id : 3 }, { id : 4 }, { id : 5 }, { id : 6 } ] expect(symmetricDifference(list1)(list2)).toEqual([ { id : 1 }, { id : 2 }, { id : 5 }, { id : 6 }, ]) }) ```

Typescript test

```typescript import {symmetricDifference} from 'rambda' describe('R.symmetricDifference', () => { it('happy', () => { const list1 = [1, 2, 3, 4] const list2 = [3, 4, 5, 6] const result = symmetricDifference(list1, list2) result // $ExpectType number[] }) it('curried', () => { const list1 = [{id: 1}, {id: 2}, {id: 3}, {id: 4}] const list2 = [{id: 3}, {id: 4}, {id: 5}, {id: 6}] const result = symmetricDifference(list1)(list2) result // $ExpectType { id: number; }[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#symmetricDifference) ### T ```typescript T(): boolean ``` Try this R.T example in Rambda REPL

All Typescript definitions

```typescript T(): boolean; ```

R.T source

```javascript export function T(){ return true } ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#T) ### tail ```typescript tail(input: T): T extends [any, ...infer U] ? U : [...T] ``` It returns all but the first element of `input`. Try this R.tail example in Rambda REPL

All Typescript definitions

```typescript tail(input: T): T extends [any, ...infer U] ? U : [...T]; tail(input: string): string; ```

R.tail source

```javascript import { drop } from './drop.js' export function tail(listOrString){ return drop(1, listOrString) } ```

Tests

```javascript import { tail } from './tail.js' test('tail', () => { expect(tail([ 1, 2, 3 ])).toEqual([ 2, 3 ]) expect(tail([ 1, 2 ])).toEqual([ 2 ]) expect(tail([ 1 ])).toEqual([]) expect(tail([])).toEqual([]) expect(tail('abc')).toBe('bc') expect(tail('ab')).toBe('b') expect(tail('a')).toBe('') expect(tail('')).toBe('') }) ```

Typescript test

```typescript import {tail} from 'rambda' describe('R.tail', () => { it('with string', () => { const result = tail('foo') result // $ExpectType string }) it('with list - one type', () => { const result = tail([1, 2, 3]) result // $ExpectType number[] }) it('with list - mixed types', () => { const result = tail(['foo', 'bar', 1, 2, 3]) result // $ExpectType (string | number)[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#tail) ### take ```typescript take(howMany: number, input: T[]): T[] ``` It returns the first `howMany` elements of `input`. Try this R.take example in Rambda REPL

All Typescript definitions

```typescript take(howMany: number, input: T[]): T[]; take(howMany: number, input: string): string; take(howMany: number): { (input: T[]): T[]; (input: string): string; }; ```

R.take source

```javascript import baseSlice from './_internals/baseSlice.js' export function take(howMany, listOrString){ if (arguments.length === 1) return _listOrString => take(howMany, _listOrString) if (howMany < 0) return listOrString.slice() if (typeof listOrString === 'string') return listOrString.slice(0, howMany) return baseSlice( listOrString, 0, howMany ) } ```

Tests

```javascript import { take } from './take.js' test('happy', () => { const arr = [ 'foo', 'bar', 'baz' ] expect(take(1, arr)).toEqual([ 'foo' ]) expect(arr).toEqual([ 'foo', 'bar', 'baz' ]) expect(take(2)([ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar' ]) expect(take(3, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ]) expect(take(4, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ]) expect(take(3)('rambda')).toBe('ram') }) test('with negative index', () => { expect(take(-1, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) expect(take(-Infinity, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) }) test('with zero index', () => { expect(take(0, [ 1, 2, 3 ])).toEqual([]) }) ```

Typescript test

```typescript import {take} from 'rambda' const list = [1, 2, 3, 4] const str = 'foobar' const howMany = 2 describe('R.take - array', () => { it('happy', () => { const result = take(howMany, list) result // $ExpectType number[] }) it('curried', () => { const result = take(howMany)(list) result // $ExpectType number[] }) }) describe('R.take - string', () => { it('happy', () => { const result = take(howMany, str) result // $ExpectType string }) it('curried', () => { const result = take(howMany)(str) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#take) ### takeLast ```typescript takeLast(howMany: number, input: T[]): T[] ``` It returns the last `howMany` elements of `input`. Try this R.takeLast example in Rambda REPL

All Typescript definitions

```typescript takeLast(howMany: number, input: T[]): T[]; takeLast(howMany: number, input: string): string; takeLast(howMany: number): { (input: T[]): T[]; (input: string): string; }; ```

R.takeLast source

```javascript import baseSlice from './_internals/baseSlice.js' export function takeLast(howMany, listOrString){ if (arguments.length === 1) return _listOrString => takeLast(howMany, _listOrString) const len = listOrString.length if (howMany < 0) return listOrString.slice() let numValue = howMany > len ? len : howMany if (typeof listOrString === 'string') return listOrString.slice(len - numValue) numValue = len - numValue return baseSlice( listOrString, numValue, len ) } ```

Tests

```javascript import { takeLast } from './takeLast.js' test('with arrays', () => { expect(takeLast(1, [ 'foo', 'bar', 'baz' ])).toEqual([ 'baz' ]) expect(takeLast(2)([ 'foo', 'bar', 'baz' ])).toEqual([ 'bar', 'baz' ]) expect(takeLast(3, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ]) expect(takeLast(4, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ]) expect(takeLast(10, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ]) }) test('with strings', () => { expect(takeLast(3, 'rambda')).toBe('bda') expect(takeLast(7, 'rambda')).toBe('rambda') }) test('with negative index', () => { expect(takeLast(-1, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) expect(takeLast(-Infinity, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ]) }) ```

Typescript test

```typescript import {takeLast} from 'rambda' const list = [1, 2, 3, 4] const str = 'foobar' const howMany = 2 describe('R.takeLast - array', () => { it('happy', () => { const result = takeLast(howMany, list) result // $ExpectType number[] }) it('curried', () => { const result = takeLast(howMany)(list) result // $ExpectType number[] }) }) describe('R.takeLast - string', () => { it('happy', () => { const result = takeLast(howMany, str) result // $ExpectType string }) it('curried', () => { const result = takeLast(howMany)(str) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#takeLast) ### takeLastWhile ```typescript takeLastWhile(predicate: (x: string) => boolean, input: string): string ``` Try this R.takeLastWhile example in Rambda REPL

All Typescript definitions

```typescript takeLastWhile(predicate: (x: string) => boolean, input: string): string; takeLastWhile(predicate: (x: string) => boolean): (input: string) => string; takeLastWhile(predicate: (x: T) => boolean, input: T[]): T[]; takeLastWhile(predicate: (x: T) => boolean): (input: T[]) => T[]; ```

R.takeLastWhile source

```javascript import { isArray } from './_internals/isArray.js' export function takeLastWhile(predicate, input){ if (arguments.length === 1){ return _input => takeLastWhile(predicate, _input) } if (input.length === 0) return input const toReturn = [] let counter = input.length while (counter){ const item = input[ --counter ] if (!predicate(item)){ break } toReturn.push(item) } return isArray(input) ? toReturn.reverse() : toReturn.reverse().join('') } ```

Tests

```javascript import { takeLastWhile } from './takeLastWhile.js' const assert = require('assert') const list = [ 1, 2, 3, 4 ] test('happy', () => { const predicate = x => x > 2 const result = takeLastWhile(predicate, list) expect(result).toEqual([ 3, 4 ]) }) test('predicate is always true', () => { const predicate = () => true const result = takeLastWhile(predicate)(list) expect(result).toEqual(list) }) test('predicate is always false', () => { const predicate = () => false const result = takeLastWhile(predicate, list) expect(result).toEqual([]) }) test('with string', () => { const result = takeLastWhile(x => x !== 'F', 'FOOBAR') expect(result).toBe('OOBAR') }) ```

Typescript test

```typescript import {takeLastWhile} from 'rambda' const list = [1, 2, 3] const str = 'FOO' describe('R.takeLastWhile', () => { it('with array', () => { const result = takeLastWhile(x => x > 1, list) result // $ExpectType number[] }) it('with array - curried', () => { const result = takeLastWhile(x => x > 1, list) result // $ExpectType number[] }) it('with string', () => { const result = takeLastWhile(x => x !== 'F', str) result // $ExpectType string }) it('with string - curried', () => { const result = takeLastWhile(x => x !== 'F')(str) result // $ExpectType string }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#takeLastWhile) ### takeWhile Try this R.takeWhile example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#takeWhile) ### tap ```typescript tap(fn: (x: T) => void, input: T): T ``` It applies function `fn` to input `x` and returns `x`. One use case is debugging in the middle of `R.compose`. Try this R.tap example in Rambda REPL

All Typescript definitions

```typescript tap(fn: (x: T) => void, input: T): T; tap(fn: (x: T) => void): (input: T) => T; ```

R.tap source

```javascript export function tap(fn, x){ if (arguments.length === 1) return _x => tap(fn, _x) fn(x) return x } ```

Tests

```javascript import { tap } from './tap.js' test('tap', () => { let a = 1 const sayX = x => a = x expect(tap(sayX, 100)).toBe(100) expect(tap(sayX)(100)).toBe(100) expect(a).toBe(100) }) ```

Typescript test

```typescript import {tap, pipe} from 'rambda' describe('R.tap', () => { it('happy', () => { pipe( tap(x => { x // $ExpectType number[] }), (x: number[]) => x.length )([1, 2]) }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#tap) ### test ```typescript test(regExpression: RegExp): (str: string) => boolean ``` It determines whether `str` matches `regExpression`. Try this R.test example in Rambda REPL

All Typescript definitions

```typescript test(regExpression: RegExp): (str: string) => boolean; test(regExpression: RegExp, str: string): boolean; ```

R.test source

```javascript export function test(pattern, str){ if (arguments.length === 1) return _str => test(pattern, _str) if (typeof pattern === 'string'){ throw new TypeError(`R.test requires a value of type RegExp as its first argument; received "${ pattern }"`) } return str.search(pattern) !== -1 } ```

Tests

```javascript import { test as testMethod } from './test.js' test('happy', () => { expect(testMethod(/^x/, 'xyz')).toBeTrue() expect(testMethod(/^y/)('xyz')).toBeFalse() }) test('throws if first argument is not regex', () => { expect(() => testMethod('foo', 'bar')).toThrowErrorMatchingInlineSnapshot('"R.test requires a value of type RegExp as its first argument; received "foo""') }) ```

Typescript test

```typescript import {test} from 'rambda' const input = 'foo ' const regex = /foo/ describe('R.test', () => { it('happy', () => { const result = test(regex, input) result // $ExpectType boolean }) it('curried', () => { const result = test(regex)(input) result // $ExpectType boolean }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#test) ### times ```typescript times(fn: (i: number) => T, howMany: number): T[] ``` It returns the result of applying function `fn` over members of range array. The range array includes numbers between `0` and `howMany`(exclusive). Try this R.times example in Rambda REPL

All Typescript definitions

```typescript times(fn: (i: number) => T, howMany: number): T[]; times(fn: (i: number) => T): (howMany: number) => T[]; ```

R.times source

```javascript import { isInteger } from './_internals/isInteger.js' import { map } from './map.js' import { range } from './range.js' export function times(fn, howMany){ if (arguments.length === 1) return _howMany => times(fn, _howMany) if (!isInteger(howMany) || howMany < 0){ throw new RangeError('n must be an integer') } return map(fn, range(0, howMany)) } ```

Tests

```javascript import assert from 'assert' import { identity } from './identity.js' import { times } from './times.js' test('happy', () => { const result = times(identity, 5) expect(result).toEqual([ 0, 1, 2, 3, 4 ]) }) test('with bad input', () => { assert.throws(() => { times(3)('cheers!') }, RangeError) assert.throws(() => { times(identity, -1) }, RangeError) }) test('curry', () => { const result = times(identity)(5) expect(result).toEqual([ 0, 1, 2, 3, 4 ]) }) ```

Typescript test

```typescript import {times, identity} from 'rambda' describe('R.times', () => { it('happy', () => { const result = times(identity, 5) result // $ExpectType number[] }) }) ```

[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#times) ### toLower ```typescript toLower(str: S): Lowercase ``` Try this R.toLower example in Rambda REPL

All Typescript definitions
```typescript toLower~~(str: S): Lowercase~~; toLower(str: string): string; ```~~~~

R.toLower source
```javascript export function toLower(str){ return str.toLowerCase() } ```

Tests
```javascript import { toLower } from './toLower.js' test('toLower', () => { expect(toLower('FOO|BAR|BAZ')).toBe('foo|bar|baz') }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#toLower) ### toPairs ```typescript toPairs>(obj: O): Array<{ [key in K]: [`${key}`, O[key]] }[K]> ``` It transforms an object to a list. Try this R.toPairs example in Rambda REPL

All Typescript definitions
```typescript toPairs>(obj: O): Array<{ [key in K]: [`${key}`, O[key]] }[K]>; toPairs~~(obj: Record): Array<[string, S]>; ```~~

R.toPairs source
```javascript export function toPairs(obj){ return Object.entries(obj) } ```

Tests
```javascript import { toPairs } from './toPairs.js' const obj = { a : 1, b : 2, c : [ 3, 4 ], } const expected = [ [ 'a', 1 ], [ 'b', 2 ], [ 'c', [ 3, 4 ] ], ] test('happy', () => { expect(toPairs(obj)).toEqual(expected) }) ```

Typescript test
```typescript import {toPairs} from 'rambda' const obj = { a: 1, b: 2, c: [3, 4], } describe('R.toPairs', () => { it('happy', () => { const result = toPairs(obj) result // $ExpectType (["b", number] | ["a", number] | ["c", number[]])[] }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#toPairs) ### toString ```typescript toString(x: unknown): string ``` Try this R.toString example in Rambda REPL

All Typescript definitions
```typescript toString(x: unknown): string; ```

R.toString source
```javascript export function toString(x){ return x.toString() } ```

Tests
```javascript import { toString } from './toString.js' test('happy', () => { expect(toString([ 1, 2, 3 ])).toBe('1,2,3') }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#toString) ### toUpper ```typescript toUpper(str: S): Uppercase ``` Try this R.toUpper example in Rambda REPL

All Typescript definitions
```typescript toUpper~~(str: S): Uppercase~~; toUpper(str: string): string; ```~~~~

R.toUpper source
```javascript export function toUpper(str){ return str.toUpperCase() } ```

Tests
```javascript import { toUpper } from './toUpper.js' test('toUpper', () => { expect(toUpper('foo|bar|baz')).toBe('FOO|BAR|BAZ') }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#toUpper) ### transpose ```typescript transpose(list: (T[])[]): (T[])[] ``` Try this R.transpose example in Rambda REPL

All Typescript definitions
```typescript transpose(list: (T[])[]): (T[])[]; ```

R.transpose source
```javascript import { isArray } from './_internals/isArray.js' export function transpose(array){ return array.reduce((acc, el) => { el.forEach((nestedEl, i) => isArray(acc[ i ]) ? acc[ i ].push(nestedEl) : acc.push([ nestedEl ])) return acc }, []) } ```

Tests
```javascript import { transpose } from './transpose.js' test('happy', () => { const input = [ [ 'a', 1 ], [ 'b', 2 ], [ 'c', 3 ], ] expect(transpose(input)).toEqual([ [ 'a', 'b', 'c' ], [ 1, 2, 3 ], ]) }) test('when rows are shorter', () => { const actual = transpose([ [ 10, 11 ], [ 20 ], [], [ 30, 31, 32 ] ]) const expected = [ [ 10, 20, 30 ], [ 11, 31 ], [ 32 ] ] expect(actual).toEqual(expected) }) test('with empty array', () => { expect(transpose([])).toEqual([]) }) test('array with falsy values', () => { const actual = transpose([ [ true, false, undefined, null ], [ null, undefined, false, true ], ]) const expected = [ [ true, null ], [ false, undefined ], [ undefined, false ], [ null, true ], ] expect(actual).toEqual(expected) }) ```

Typescript test
```typescript import {transpose} from 'rambda' const input = [ ['a', 1], ['b', 2], ['c', 3], ] describe('R.transpose', () => { it('happy', () => { const result = transpose(input) result // $ExpectType (string | number)[][] }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#transpose) ### trim ```typescript trim(str: string): string ``` Try this R.trim example in Rambda REPL

All Typescript definitions
```typescript trim(str: string): string; ```

R.trim source
```javascript export function trim(str){ return str.trim() } ```

Tests
```javascript import { trim } from './trim.js' test('trim', () => { expect(trim(' foo ')).toBe('foo') }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#trim) ### tryCatch It returns function that runs `fn` in `try/catch` block. If there was an error, then `fallback` is used to return the result. Note that `fn` can be value or asynchronous/synchronous function(unlike `Ramda` where fallback can only be a synchronous function). Try this R.tryCatch example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#tryCatch) ### type It accepts any input and it returns its type. Try this R.type example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#type) ### unapply ```typescript unapply(fn: (args: any[]) => T): (...args: any[]) => T ``` It calls a function `fn` with the list of values of the returned function. `R.unapply` is the opposite of `R.apply` method. Try this R.unapply example in Rambda REPL

All Typescript definitions
```typescript unapply(fn: (args: any[]) => T): (...args: any[]) => T; ```

R.unapply source
```javascript export function unapply(fn){ return function (...args){ return fn.call(this, args) } } ```

Tests
```javascript import { apply } from './apply.js' import { converge } from './converge.js' import { identity } from './identity.js' import { prop } from './prop.js' import { sum } from './sum.js' import { unapply } from './unapply.js' test('happy', () => { const fn = unapply(identity) expect(fn( 1, 2, 3 )).toEqual([ 1, 2, 3 ]) expect(fn()).toEqual([]) }) test('returns a function which is always passed one argument', () => { const fn = unapply(function (){ return arguments.length }) expect(fn('x')).toBe(1) expect(fn('x', 'y')).toBe(1) expect(fn( 'x', 'y', 'z' )).toBe(1) }) test('forwards arguments to decorated function as an array', () => { const fn = unapply(xs => '[' + xs + ']') expect(fn(2)).toBe('[2]') expect(fn(2, 4)).toBe('[2,4]') expect(fn( 2, 4, 6 )).toBe('[2,4,6]') }) test('returns a function with length 0', () => { const fn = unapply(identity) expect(fn).toHaveLength(0) }) test('is the inverse of R.apply', () => { let a, b, c, d, e, f, g, n const rand = function (){ return Math.floor(200 * Math.random()) - 100 } f = Math.max g = unapply(apply(f)) n = 1 while (n <= 100){ a = rand() b = rand() c = rand() d = rand() e = rand() expect(f( a, b, c, d, e )).toEqual(g( a, b, c, d, e )) n += 1 } f = function (xs){ return '[' + xs + ']' } g = apply(unapply(f)) n = 1 while (n <= 100){ a = rand() b = rand() c = rand() d = rand() e = rand() expect(f([ a, b, c, d, e ])).toEqual(g([ a, b, c, d, e ])) n += 1 } }) test('it works with converge', () => { const fn = unapply(sum) const convergeFn = converge(fn, [ prop('a'), prop('b'), prop('c') ]) const obj = { a : 1337, b : 42, c : 1, } const expected = 1337 + 42 + 1 expect(convergeFn(obj)).toEqual(expected) }) ```

Typescript test
```typescript import {join, unapply, sum} from 'rambda' describe('R.unapply', () => { it('happy', () => { const fn = unapply(sum) fn(1, 2, 3) // $ExpectType number }) it('joins a string', () => { const fn = unapply(join('')) fn('s', 't', 'r', 'i', 'n', 'g') // $ExpectType string }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#unapply) ### union ```typescript union(x: T[], y: T[]): T[] ``` It takes two lists and return a new list containing a merger of both list with removed duplicates. `R.equals` is used to compare for duplication. Try this R.union example in Rambda REPL

All Typescript definitions
```typescript union(x: T[], y: T[]): T[]; union(x: T[]): (y: T[]) => T[]; ```

R.union source
```javascript import { cloneList } from './_internals/cloneList.js' import { includes } from './includes.js' export function union(x, y){ if (arguments.length === 1) return _y => union(x, _y) const toReturn = cloneList(x) y.forEach(yInstance => { if (!includes(yInstance, x)) toReturn.push(yInstance) }) return toReturn } ```

Tests
```javascript import { union } from './union.js' test('happy', () => { expect(union([ 1, 2 ], [ 2, 3 ])).toEqual([ 1, 2, 3 ]) }) test('with list of objects', () => { const list1 = [ { a : 1 }, { a : 2 } ] const list2 = [ { a : 2 }, { a : 3 } ] const result = union(list1)(list2) }) ```

Typescript test
```typescript import {union} from 'rambda' describe('R.union', () => { it('happy', () => { const result = union([1, 2], [2, 3]) result // $ExpectType number[] }) it('with array of objects - case 1', () => { const list1 = [{a: 1}, {a: 2}] const list2 = [{a: 2}, {a: 3}] const result = union(list1, list2) result // $ExpectType { a: number; }[] }) it('with array of objects - case 2', () => { const list1 = [{a: 1, b: 1}, {a: 2}] const list2 = [{a: 2}, {a: 3, b: 3}] const result = union(list1, list2) result[0].a // $ExpectType number result[0].b // $ExpectType number | undefined }) }) describe('R.union - curried', () => { it('happy', () => { const result = union([1, 2])([2, 3]) result // $ExpectType number[] }) it('with array of objects - case 1', () => { const list1 = [{a: 1}, {a: 2}] const list2 = [{a: 2}, {a: 3}] const result = union(list1)(list2) result // $ExpectType { a: number; }[] }) it('with array of objects - case 2', () => { const list1 = [{a: 1, b: 1}, {a: 2}] const list2 = [{a: 2}, {a: 3, b: 3}] const result = union(list1)(list2) result[0].a // $ExpectType number result[0].b // $ExpectType number | undefined }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#union) ### uniq ```typescript uniq(list: T[]): T[] ``` It returns a new array containing only one copy of each element of `list`. `R.equals` is used to determine equality. Try this R.uniq example in Rambda REPL

All Typescript definitions
```typescript uniq(list: T[]): T[]; ```

R.uniq source
```javascript import { _Set } from './_internals/set.js' export function uniq(list){ const set = new _Set() const willReturn = [] list.forEach(item => { if (set.checkUniqueness(item)){ willReturn.push(item) } }) return willReturn } ```

Tests
```javascript import { uniq } from './uniq.js' test('happy', () => { const list = [ 1, 2, 3, 3, 3, 1, 2, 0 ] expect(uniq(list)).toEqual([ 1, 2, 3, 0 ]) }) test('with object', () => { const list = [ { a : 1 }, { a : 2 }, { a : 1 }, { a : 2 } ] expect(uniq(list)).toEqual([ { a : 1 }, { a : 2 } ]) }) test('with nested array', () => { expect(uniq([ [ 42 ], [ 42 ] ])).toEqual([ [ 42 ] ]) }) test('with booleans', () => { expect(uniq([ [ false ], [ false ], [ true ] ])).toEqual([ [ false ], [ true ] ]) }) test('with falsy values', () => { expect(uniq([ undefined, null ])).toEqual([ undefined, null ]) }) test('can distinct between string and number', () => { expect(uniq([ 1, '1' ])).toEqual([ 1, '1' ]) }) ```

Typescript test
```typescript import {uniq} from 'rambda' describe('R.uniq', () => { it('happy', () => { const result = uniq([1, 2, 3, 3, 3, 1, 2, 0]) result // $ExpectType number[] }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#uniq) ### uniqBy It applies uniqueness to input list based on function that defines what to be used for comparison between elements. `R.equals` is used to determine equality. Try this R.uniqBy example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#uniqBy) ### uniqWith ```typescript uniqWith(predicate: (x: T, y: T) => boolean, list: T[]): T[] ``` It returns a new array containing only one copy of each element in `list` according to `predicate` function. This predicate should return true, if two elements are equal. Try this R.uniqWith example in Rambda REPL

All Typescript definitions
```typescript uniqWith(predicate: (x: T, y: T) => boolean, list: T[]): T[]; uniqWith(predicate: (x: T, y: T) => boolean): (list: T[]) => T[]; ```

R.uniqWith source
```javascript function includesWith( predicate, target, list ){ let willReturn = false let index = -1 while (++index < list.length && !willReturn){ const value = list[ index ] if (predicate(target, value)){ willReturn = true } } return willReturn } export function uniqWith(predicate, list){ if (arguments.length === 1) return _list => uniqWith(predicate, _list) let index = -1 const willReturn = [] while (++index < list.length){ const value = list[ index ] if (!includesWith( predicate, value, willReturn )){ willReturn.push(value) } } return willReturn } ```

Tests
```javascript import { uniqWith as uniqWithRamda } from 'ramda' import { uniqWith } from './uniqWith.js' const list = [ { a : 1 }, { a : 1 } ] test('happy', () => { const fn = (x, y) => x.a === y.a const result = uniqWith(fn, list) expect(result).toEqual([ { a : 1 } ]) }) test('with list of strings', () => { const fn = (x, y) => x.length === y.length const list = [ '0', '11', '222', '33', '4', '55' ] const result = uniqWith(fn)(list) const resultRamda = uniqWithRamda(fn, list) expect(result).toEqual([ '0', '11', '222' ]) expect(resultRamda).toEqual([ '0', '11', '222' ]) }) ```

Typescript test
```typescript import {uniqWith} from 'rambda' describe('R.uniqWith', () => { it('happy', () => { const list = [{a: 1}, {a: 1}] const fn = (x: any, y: any) => x.a === y.a const result = uniqWith(fn, list) result // $ExpectType { a: number; }[] }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#uniqWith) ### unless ```typescript unless(predicate: (x: T) => boolean, whenFalseFn: (x: T) => U, x: T): T | U ``` The method returns function that will be called with argument `input`. If `predicate(input)` returns `false`, then the end result will be the outcome of `whenFalse(input)`. In the other case, the final output will be the `input` itself. Try this R.unless example in Rambda REPL

All Typescript definitions
```typescript unless(predicate: (x: T) => boolean, whenFalseFn: (x: T) => U, x: T): T | U; unless(predicate: (x: T) => boolean, whenFalseFn: (x: T) => U): (x: T) => T | U; unless(predicate: (x: T) => boolean, whenFalseFn: (x: T) => T, x: T): T; unless(predicate: (x: T) => boolean, whenFalseFn: (x: T) => T): (x: T) => T; ```

R.unless source
```javascript export function unless(predicate, whenFalse){ if (arguments.length === 1){ return _whenFalse => unless(predicate, _whenFalse) } return input => predicate(input) ? input : whenFalse(input) } ```

Tests
```javascript import { inc } from './inc.js' import { isNil } from './isNil.js' import { unless } from './unless.js' test('happy', () => { const safeInc = unless(isNil, inc) expect(safeInc(null)).toBeNull() expect(safeInc(1)).toBe(2) }) test('curried', () => { const safeIncCurried = unless(isNil)(inc) expect(safeIncCurried(null)).toBeNull() }) ```

Typescript test
```typescript import {unless, inc} from 'rambda' describe('R.unless', () => { it('happy', () => { const fn = unless(x => x > 5, inc) const result = fn(1) result // $ExpectType number }) it('with one explicit type', () => { const result = unless( x => { x // $ExpectType number return x > 5 }, x => { x // $ExpectType number return x + 1 }, 1 ) result // $ExpectType number }) it('with two different explicit types', () => { const result = unless( x => { x // $ExpectType number return x > 5 }, x => { x // $ExpectType number return `${x}-foo` }, 1 ) result // $ExpectType string | number }) }) describe('R.unless - curried', () => { it('happy', () => { const fn = unless(x => x > 5, inc) const result = fn(1) result // $ExpectType number }) it('with one explicit type', () => { const fn = unless( x => { x // $ExpectType number return x > 5 }, x => { x // $ExpectType number return x + 1 } ) const result = fn(1) result // $ExpectType number }) it('with two different explicit types', () => { const fn = unless( x => { x // $ExpectType number return x > 5 }, x => { x // $ExpectType number return `${x}-foo` } ) const result = fn(1) result // $ExpectType string | number }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#unless) ### unnest [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#unnest) ### unwind Try this R.unwind example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#unwind) ### update ```typescript update(index: number, newValue: T, list: T[]): T[] ``` It returns a copy of `list` with updated element at `index` with `newValue`. Try this R.update example in Rambda REPL

All Typescript definitions
```typescript update(index: number, newValue: T, list: T[]): T[]; update(index: number, newValue: T): (list: T[]) => T[]; ```

R.update source
```javascript import { cloneList } from './_internals/cloneList.js' import { curry } from './curry.js' export function updateFn( index, newValue, list ){ const clone = cloneList(list) if (index === -1) return clone.fill(newValue, index) return clone.fill( newValue, index, index + 1 ) } export const update = curry(updateFn) ```

Tests
```javascript import { update } from './update.js' const list = [ 1, 2, 3 ] test('happy', () => { const newValue = 8 const index = 1 const result = update( index, newValue, list ) const curriedResult = update(index, newValue)(list) const tripleCurriedResult = update(index)(newValue)(list) const expected = [ 1, 8, 3 ] expect(result).toEqual(expected) expect(curriedResult).toEqual(expected) expect(tripleCurriedResult).toEqual(expected) }) test('list has no such index', () => { const newValue = 8 const index = 10 const result = update( index, newValue, list ) expect(result).toEqual(list) }) test('with negative index', () => { expect(update( -1, 10, [ 1 ] )).toEqual([ 10 ]) expect(update( -1, 10, [] )).toEqual([]) expect(update( -1, 10, list )).toEqual([ 1, 2, 10 ]) expect(update( -2, 10, list )).toEqual([ 1, 10, 3 ]) expect(update( -3, 10, list )).toEqual([ 10, 2, 3 ]) }) ```

Typescript test
```typescript import {update} from 'rambda' describe('R.update', () => { it('happy', () => { const result = update(1, 0, [1, 2, 3]) result // $ExpectType number[] }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#update) ### values ```typescript values(obj: T): T[K][] ``` With correct input, this is nothing more than `Object.values(Record)`. If `obj` is not an object, then it returns an empty array. Try this R.values example in Rambda REPL

All Typescript definitions
```typescript values(obj: T): T[K][]; ```

R.values source
```javascript import { type } from './type.js' export function values(obj){ if (type(obj) !== 'Object') return [] return Object.values(obj) } ```

Tests
```javascript import { values } from './values.js' test('happy', () => { expect(values({ a : 1, b : 2, c : 3, })).toEqual([ 1, 2, 3 ]) }) test('with bad input', () => { expect(values(null)).toEqual([]) expect(values(undefined)).toEqual([]) expect(values(55)).toEqual([]) expect(values('foo')).toEqual([]) expect(values(true)).toEqual([]) expect(values(false)).toEqual([]) expect(values(NaN)).toEqual([]) expect(values(Infinity)).toEqual([]) expect(values([])).toEqual([]) }) ```

Typescript test
```typescript import {values} from 'rambda' describe('R.values', () => { it('happy', () => { const result = values({ a: 1, b: 2, c: 3, }) result // $ExpectType number[] }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#values) ### view ```typescript view(lens: Lens): (target: T) => U ``` It returns the value of `lens` focus over `target` object. Try this R.view example in Rambda REPL

All Typescript definitions
```typescript view(lens: Lens): (target: T) => U; view(lens: Lens, target: T): U; ```

R.view source
```javascript const Const = x => ({ x, map : fn => Const(x), }) export function view(lens, target){ if (arguments.length === 1) return _target => view(lens, _target) return lens(Const)(target).x } ```

Tests
```javascript import { assoc } from './assoc.js' import { lens } from './lens.js' import { prop } from './prop.js' import { view } from './view.js' const testObject = { foo : 'Led Zeppelin' } const assocLens = lens(prop('foo'), assoc('foo')) test('happy', () => { expect(view(assocLens, testObject)).toBe('Led Zeppelin') }) ```

Typescript test
```typescript import {lens, view, assoc} from 'rambda' interface Input { foo: string, } const testObject: Input = { foo: 'Led Zeppelin', } const fooLens = lens((x: Input) => { return x.foo }, assoc('foo')) describe('R.view', () => { it('happt', () => { const result = view(fooLens, testObject) result // $ExpectType string }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#view) ### when ```typescript when(predicate: (x: T) => boolean, whenTrueFn: (a: T) => U, input: T): T | U ```

All Typescript definitions
```typescript when(predicate: (x: T) => boolean, whenTrueFn: (a: T) => U, input: T): T | U; when(predicate: (x: T) => boolean, whenTrueFn: (a: T) => U): (input: T) => T | U; when(predicate: (x: T) => boolean): ((whenTrueFn: (a: T) => U) => (input: T) => T | U); ```

R.when source
```javascript import { curry } from './curry.js' function whenFn( predicate, whenTrueFn, input ){ if (!predicate(input)) return input return whenTrueFn(input) } export const when = curry(whenFn) ```

Tests
```javascript import { add } from './add.js' import { when } from './when.js' const predicate = x => typeof x === 'number' test('happy', () => { const fn = when(predicate, add(11)) expect(fn(11)).toBe(22) expect(fn('foo')).toBe('foo') }) ```

Typescript test
```typescript import {when} from 'rambda' const predicate = (x: number) => x > 2 const whenTrueFn = (x: number) => String(x) describe('R.when', () => { it('happy', () => { const result = when(predicate, whenTrueFn, 1) result // $ExpectType string | 1 }) it('curry 1', () => { const fn = when(predicate, whenTrueFn) const result = fn(1) result // $ExpectType string | number }) it('curry 2 require explicit types', () => { const fn = when(predicate)(whenTrueFn) const result = fn(1) result // $ExpectType string | number }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#when) ### where ```typescript where(conditions: T, input: U): boolean ``` It returns `true` if all each property in `conditions` returns `true` when applied to corresponding property in `input` object. Try this R.where example in Rambda REPL

All Typescript definitions
```typescript where(conditions: T, input: U): boolean; where(conditions: T): (input: U) => boolean; where(conditions: ObjFunc2, input: U): boolean; where(conditions: ObjFunc2): (input: U) => boolean; ```

R.where source
```javascript export function where(conditions, input){ if (input === undefined){ return _input => where(conditions, _input) } let flag = true for (const prop in conditions){ if (!flag) continue const result = conditions[ prop ](input[ prop ]) if (flag && result === false){ flag = false } } return flag } ```

Tests
```javascript import { equals } from './equals.js' import { where } from './where.js' test('when true', () => { const result = where({ a : equals('foo'), b : equals('bar'), }, { a : 'foo', b : 'bar', x : 11, y : 19, }) expect(result).toBeTrue() }) test('when false | early exit', () => { let counter = 0 const equalsFn = expected => input => { console.log(expected, 'expected') counter++ return input === expected } const predicate = where({ a : equalsFn('foo'), b : equalsFn('baz'), }) expect(predicate({ a : 'notfoo', b : 'notbar', })).toBeFalse() expect(counter).toBe(1) }) ```

Typescript test
```typescript import {where, equals} from 'rambda' describe('R.where', () => { it('happy', () => { const input = { a: 'foo', b: 'bar', x: 11, y: 19, } const conditions = { a: equals('foo'), b: equals('bar'), } const result = where(conditions, input) const curriedResult = where(conditions)(input) result // $ExpectType boolean curriedResult // $ExpectType boolean }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#where) ### whereAny Same as `R.where`, but it will return `true` if at least one condition check returns `true`. Try this R.whereAny example in Rambda REPL [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#whereAny) ### whereEq ```typescript whereEq(condition: T, input: U): boolean ``` It will return `true` if all of `input` object fully or partially include `rule` object. `R.equals` is used to determine equality. Try this R.whereEq example in Rambda REPL

All Typescript definitions
```typescript whereEq(condition: T, input: U): boolean; whereEq(condition: T): (input: U) => boolean; ```

R.whereEq source
```javascript import { equals } from './equals.js' import { filter } from './filter.js' export function whereEq(condition, input){ if (arguments.length === 1){ return _input => whereEq(condition, _input) } const result = filter((conditionValue, conditionProp) => equals(conditionValue, input[ conditionProp ]), condition) return Object.keys(result).length === Object.keys(condition).length } ```

Tests
```javascript import { whereEq } from './whereEq.js' test('when true', () => { const condition = { a : 1 } const input = { a : 1, b : 2, } const result = whereEq(condition, input) const expectedResult = true expect(result).toEqual(expectedResult) }) test('when false', () => { const condition = { a : 1 } const input = { b : 2 } const result = whereEq(condition, input) const expectedResult = false expect(result).toEqual(expectedResult) }) test('with nested object', () => { const condition = { a : { b : 1 } } const input = { a : { b : 1 }, c : 2, } const result = whereEq(condition)(input) const expectedResult = true expect(result).toEqual(expectedResult) }) test('with wrong input', () => { const condition = { a : { b : 1 } } expect(() => whereEq(condition, null)).toThrowErrorMatchingInlineSnapshot('"Cannot read properties of null (reading \'a\')"') }) ```

Typescript test
```typescript import {whereEq} from 'rambda' describe('R.whereEq', () => { it('happy', () => { const result = whereEq({a: {b: 2}}, {b: 2}) const curriedResult = whereEq({a: {b: 2}})({b: 2}) result // $ExpectType boolean curriedResult // $ExpectType boolean }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#whereEq) ### without ```typescript without(matchAgainst: T[], source: T[]): T[] ``` It will return a new array, based on all members of `source` list that are not part of `matchAgainst` list. `R.equals` is used to determine equality. Try this R.without example in Rambda REPL

All Typescript definitions
```typescript without(matchAgainst: T[], source: T[]): T[]; without(matchAgainst: T[]): (source: T[]) => T[]; ```

R.without source
```javascript import { _indexOf } from './equals.js' import { reduce } from './reduce.js' export function without(matchAgainst, source){ if (source === undefined){ return _source => without(matchAgainst, _source) } return reduce( (prev, current) => _indexOf(current, matchAgainst) > -1 ? prev : prev.concat(current), [], source ) } ```

Tests
```javascript import { without as withoutRamda } from 'ramda' import { without } from './without.js' test('should return a new list without values in the first argument', () => { const itemsToOmit = [ 'A', 'B', 'C' ] const collection = [ 'A', 'B', 'C', 'D', 'E', 'F' ] expect(without(itemsToOmit, collection)).toEqual([ 'D', 'E', 'F' ]) expect(without(itemsToOmit)(collection)).toEqual([ 'D', 'E', 'F' ]) }) test('with list of objects', () => { const itemsToOmit = [ { a : 1 }, { c : 3 } ] const collection = [ { a : 1 }, { b : 2 }, { c : 3 }, { d : 4 } ] const expected = [ { b : 2 }, { d : 4 } ] expect(without(itemsToOmit, collection)).toEqual(expected) expect(withoutRamda(itemsToOmit, collection)).toEqual(expected) }) test('ramda accepts string as target input while rambda throws', () => { expect(withoutRamda('0:1', [ '0', '0:1' ])).toEqual([]) expect(() => without('0:1', [ '0', '0:1' ])).toThrowErrorMatchingInlineSnapshot('"Cannot read property \'indexOf\' of 0:1"') expect(without([ '0:1' ], [ '0', '0:1' ])).toEqual([ '0' ]) }) test('ramda test', () => { expect(without([ 1, 2 ])([ 1, 2, 1, 3, 4 ])).toEqual([ 3, 4 ]) }) ```

Typescript test
```typescript import {without} from 'rambda' const itemsToOmit = ['A', 'B', 'C'] const collection = ['A', 'B', 'C', 'D', 'E', 'F'] describe('R.without', () => { it('happy', () => { const result = without(itemsToOmit, collection) result // $ExpectType string[] }) it('curried', () => { const result = without(itemsToOmit)(collection) result // $ExpectType string[] }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#without) ### xor ```typescript xor(x: boolean, y: boolean): boolean ``` Logical XOR Try this R.xor example in Rambda REPL

All Typescript definitions
```typescript xor(x: boolean, y: boolean): boolean; xor(y: boolean): (y: boolean) => boolean; ```

R.xor source
```javascript export function xor(a, b){ if (arguments.length === 1) return _b => xor(a, _b) return Boolean(a) && !b || Boolean(b) && !a } ```

Tests
```javascript import { xor } from './xor.js' test('compares two values with exclusive or', () => { expect(xor(true, true)).toBeFalse() expect(xor(true, false)).toBeTrue() expect(xor(false, true)).toBeTrue() expect(xor(false, false)).toBeFalse() }) test('when both values are truthy, it should return false', () => { expect(xor(true, 'foo')).toBeFalse() expect(xor(42, true)).toBeFalse() expect(xor('foo', 42)).toBeFalse() expect(xor({}, true)).toBeFalse() expect(xor(true, [])).toBeFalse() expect(xor([], {})).toBeFalse() expect(xor(new Date(), true)).toBeFalse() expect(xor(true, Infinity)).toBeFalse() expect(xor(Infinity, new Date())).toBeFalse() }) test('when both values are falsy, it should return false', () => { expect(xor(null, false)).toBeFalse() expect(xor(false, undefined)).toBeFalse() expect(xor(undefined, null)).toBeFalse() expect(xor(0, false)).toBeFalse() expect(xor(false, NaN)).toBeFalse() expect(xor(NaN, 0)).toBeFalse() expect(xor('', false)).toBeFalse() }) test('when one argument is truthy and the other is falsy, it should return true', () => { expect(xor('foo', null)).toBeTrue() expect(xor(null, 'foo')).toBeTrue() expect(xor(undefined, 42)).toBeTrue() expect(xor(42, undefined)).toBeTrue() expect(xor(Infinity, NaN)).toBeTrue() expect(xor(NaN, Infinity)).toBeTrue() expect(xor({}, '')).toBeTrue() expect(xor('', {})).toBeTrue() expect(xor(new Date(), 0)).toBeTrue() expect(xor(0, new Date())).toBeTrue() expect(xor([], null)).toBeTrue() expect(xor(undefined, [])).toBeTrue() }) ```

Typescript test
```typescript import {xor} from 'rambda' describe('R.xor', () => { it('happy', () => { xor(true, false) // $ExpectType boolean }) it('curry', () => { xor(true)(false) // $ExpectType boolean }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#xor) ### zip ```typescript zip(x: K[], y: V[]): KeyValuePair[] ``` It will return a new array containing tuples of equally positions items from both `x` and `y` lists. The returned list will be truncated to match the length of the shortest supplied list. Try this R.zip example in Rambda REPL

All Typescript definitions
```typescript zip(x: K[], y: V[]): KeyValuePair[]; zip(x: K[]): (y: V[]) => KeyValuePair[]; ```

R.zip source
```javascript export function zip(left, right){ if (arguments.length === 1) return _right => zip(left, _right) const result = [] const length = Math.min(left.length, right.length) for (let i = 0; i < length; i++){ result[ i ] = [ left[ i ], right[ i ] ] } return result } ```

Tests
```javascript import { zip } from './zip.js' const array1 = [ 1, 2, 3 ] const array2 = [ 'A', 'B', 'C' ] test('should return an array', () => { const actual = zip(array1)(array2) expect(actual).toBeInstanceOf(Array) }) test('should return and array or tuples', () => { const expected = [ [ 1, 'A' ], [ 2, 'B' ], [ 3, 'C' ], ] const actual = zip(array1, array2) expect(actual).toEqual(expected) }) test('should truncate result to length of shorted input list', () => { const expectedA = [ [ 1, 'A' ], [ 2, 'B' ], ] const actualA = zip([ 1, 2 ], array2) expect(actualA).toEqual(expectedA) const expectedB = [ [ 1, 'A' ], [ 2, 'B' ], ] const actualB = zip(array1, [ 'A', 'B' ]) expect(actualB).toEqual(expectedB) }) ```

Typescript test
```typescript import {zip} from 'rambda' describe('R.zip', () => { it('happy', () => { const array1 = [1, 2, 3] const array2 = ['A', 'B', 'C'] const result = zip(array1)(array2) result // $ExpectType KeyValuePair[] }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#zip) ### zipObj ```typescript zipObj(keys: K[], values: T[]): { [P in K]: T } ``` It will return a new object with keys of `keys` array and values of `values` array. Try this R.zipObj example in Rambda REPL

All Typescript definitions
```typescript zipObj(keys: K[], values: T[]): { [P in K]: T }; zipObj(keys: K[]): (values: T[]) => { [P in K]: T }; zipObj(keys: K[], values: T[]): { [P in K]: T }; zipObj(keys: K[]): (values: T[]) => { [P in K]: T }; ```

R.zipObj source
```javascript import { take } from './take.js' export function zipObj(keys, values){ if (arguments.length === 1) return yHolder => zipObj(keys, yHolder) return take(values.length, keys).reduce(( prev, xInstance, i ) => { prev[ xInstance ] = values[ i ] return prev }, {}) } ```

Tests
```javascript import { equals } from './equals.js' import { zipObj } from './zipObj.js' test('zipObj', () => { expect(zipObj([ 'a', 'b', 'c' ], [ 1, 2, 3 ])).toEqual({ a : 1, b : 2, c : 3, }) }) test('0', () => { expect(zipObj([ 'a', 'b' ])([ 1, 2, 3 ])).toEqual({ a : 1, b : 2, }) }) test('1', () => { expect(zipObj([ 'a', 'b', 'c' ])([ 1, 2 ])).toEqual({ a : 1, b : 2, }) }) test('ignore extra keys', () => { const result = zipObj([ 'a', 'b', 'c', 'd', 'e', 'f' ], [ 1, 2, 3 ]) const expected = { a : 1, b : 2, c : 3, } expect(equals(result, expected)).toBeTrue() }) ```

Typescript test
```typescript import {zipObj} from 'rambda' describe('R.zipObj', () => { it('happy', () => { // this is wrong since 24.10.2020 `@types/ramda` changes const result = zipObj(['a', 'b', 'c', 'd'], [1, 2, 3]) result // $ExpectType { b: number; a: number; c: number; d: number; } }) it('imported from @types/ramda', () => { const result = zipObj(['a', 'b', 'c'], [1, 2, 3]) const curriedResult = zipObj(['a', 'b', 'c'])([1, 2, 3]) result // $ExpectType { b: number; a: number; c: number; } curriedResult // $ExpectType { b: number; a: number; c: number; } }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#zipObj) ### zipWith ```typescript zipWith(fn: (x: T, y: U) => TResult, list1: T[], list2: U[]): TResult[] ``` Try this R.zipWith example in Rambda REPL

All Typescript definitions
```typescript zipWith(fn: (x: T, y: U) => TResult, list1: T[], list2: U[]): TResult[]; zipWith(fn: (x: T, y: U) => TResult, list1: T[]): (list2: U[]) => TResult[]; zipWith(fn: (x: T, y: U) => TResult): (list1: T[], list2: U[]) => TResult[]; ```

R.zipWith source
```javascript import { curry } from './curry.js' import { take } from './take.js' function zipWithFn( fn, x, y ){ return take(x.length > y.length ? y.length : x.length, x).map((xInstance, i) => fn(xInstance, y[ i ])) } export const zipWith = curry(zipWithFn) ```

Tests
```javascript import { add } from './add.js' import { zipWith } from './zipWith.js' const list1 = [ 1, 2, 3 ] const list2 = [ 10, 20, 30, 40 ] const list3 = [ 100, 200 ] test('when second list is shorter', () => { const result = zipWith( add, list1, list3 ) expect(result).toEqual([ 101, 202 ]) }) test('when second list is longer', () => { const result = zipWith( add, list1, list2 ) expect(result).toEqual([ 11, 22, 33 ]) }) ```

Typescript test
```typescript import {zipWith} from 'rambda' const list1 = [1, 2] const list2 = [10, 20, 30] describe('R.zipWith', () => { it('happy', () => { const result = zipWith( (x, y) => { x // $ExpectType number y // $ExpectType number return `${x}-${y}` }, list1, list2 ) result // $ExpectType string[] }) it('curried', () => { const result = zipWith((x, y) => { x // $ExpectType unknown y // $ExpectType unknown return `${x}-${y}` })(list1, list2) result // $ExpectType string[] }) }) ```
[![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#zipWith) ## ❯ CHANGELOG 7.5.0 - IMPORTANT: Remove `export` property in `package.json` in order to allow `Rambda` support for projects with `"type": "module"` in `package.json` - [Issue #667](https://github.com/selfrefactor/rambda/issues/657) - Add `R.unnest` - [Rambdax issue 89](https://github.com/selfrefactor/rambdax/issues/89) - `R.uniq` is not using `R.equals` as Ramda does - [Issue #88](https://github.com/selfrefactor/rambdax/issues/88) - Fix `R.path(['non','existing','path'], obj)` TS definition as 7.4.0 release caused TS errors - [Issue #668](https://github.com/selfrefactor/rambda/issues/668) 7.4.0 - Synchronize with `@types/ramda` - `R.prop`, `R.path`, `R.pickAll` - Remove `esm` Rollup output due to tree-shaking issues. - Upgrade all dev dependencies. 7.3.0 - Important - changing import declaration in `package.json` in order to fix tree-shaking issue - [Issue #647](https://github.com/selfrefactor/rambda/issues/647) - Add `R.modify` - Allow multiple inputs in Typescript versions of `R.anyPass` and `R.allPass` - [Issue #642](https://github.com/selfrefactor/rambda/issues/604) - Using wrong clone of object in `R.mergeDeepRight` - [Issue #650](https://github.com/selfrefactor/rambda/issues/650) - Missing early return in `R.where` - [Issue #648](https://github.com/selfrefactor/rambda/issues/648) - `R.allPass` doesn't accept more than 1 parameters for function predicates- [Issue #604](https://github.com/selfrefactor/rambda/issues/604) 7.2.1 - Remove bad typings of `R.propIs` which caused the library to cannot be build with Typescript. - Drop support for `Wallaby` as per [https://github.com/wallabyjs/public/issues/3037](https://github.com/wallabyjs/public/issues/3037) 7.2.0 - Wrong `R.update` if index is `-1` - [PR #593](https://github.com/selfrefactor/rambda/pull/593) - Wrong curried typings in `R.anyPass` - [Issue #642](https://github.com/selfrefactor/rambda/issues/642) - `R.modifyPath` not exported - [Issue #640](https://github.com/selfrefactor/rambda/issues/640) - Add new method `R.uniqBy`. Implementation is coming from [Ramda MR#2641](https://github.com/ramda/ramda/pull/2641) - Apply the following changes from `@types/rambda`: -- [https://github.com/DefinitelyTyped/DefinitelyTyped/commit/bab47272d52fc7bb81e85da36dbe9c905a04d067](add `AnyFunction` and `AnyConstructor`) -- Improve `R.ifElse` typings - https://github.com/DefinitelyTyped/DefinitelyTyped/pull/59291 -- Make `R.propEq` safe for `null/undefined` arguments - https://github.com/ramda/ramda/pull/2594/files 7.1.4 - `R.mergeRight` not found on `Deno` import - [Issue #633](https://github.com/selfrefactor/rambda/issues/633) 7.1.0 - Add `R.mergeRight` - introduced by Ramda's latest release. While Ramda renames `R.merge`, Rambda will keep `R.merge`. - Rambda's `pipe/compose` doesn't return proper length of composed function which leads to issue with `R.applySpec`. It was fixed by using Ramda's `pipe/compose` logic - [Issue #627](https://github.com/selfrefactor/rambda/issues/627) - Replace `Async` with `Promise` as return type of `R.type`. - Add new types as Typescript output for `R.type` - "Map", "WeakMap", "Generator", "GeneratorFunction", "BigInt", "ArrayBuffer" - Add `R.juxt` method - Add `R.propSatisfies` method - Add new methods after `Ramda` version upgrade to `0.28.0`: -- R.count -- R.modifyPath -- R.on -- R.whereAny -- R.partialObject 7.0.3 Rambda.none has wrong logic introduced in version `7.0.0` - [Issue #625](https://github.com/selfrefactor/rambda/issues/625) 7.0.2 Rambda doesn't work with `pnpm` due to wrong export configuration - [Issue #619](https://github.com/selfrefactor/rambda/issues/619) 7.0.1 - Wrong ESM export configuration in `package.json` - [Issue #614](https://github.com/selfrefactor/rambda/issues/614) 7.0.0 - Breaking change - sync `R.compose`/`R.pipe` with `@types/ramda`. That is significant change so as safeguard, it will lead a major bump. Important - this lead to raising required Typescript version to `4.2.2`. In other words, to use `Rambda` you'll need Typescript version `4.2.2` or newer. Related commit in `@types/ramda` - https://github.com/DefinitelyTyped/DefinitelyTyped/commit/286eff4f76d41eb8f091e7437eabd8a60d97fc1f#diff-4f74803fa83a81e47cb17a7d8a4e46a7e451f4d9e5ce2f1bd7a70a72d91f4bc1 There are several other changes in `@types/ramda` as stated in [this comment](https://github.com/ramda/ramda/issues/2976#issuecomment-990408945). This leads to change of typings for the following methods in **Rambda**: -- R.unless -- R.toString -- R.ifElse -- R.always -- R.complement -- R.cond -- R.is -- R.sortBy -- R.dissoc -- R.toPairs -- R.assoc -- R.toLower -- R.toUpper - One more reason for the breaking change is changing of export declarations in `package.json` based on [this blog post](https://devblogs.microsoft.com/typescript/announcing-typescript-4-5-beta/#packagejson-exports-imports-and-self-referencing) and [this merged Ramda's PR](https://github.com/ramda/ramda/pull/2999). This also led to renaming of `babel.config.js` to `babel.config.cjs`. - Add `R.apply`, `R.bind` and `R.unapply` - `R.startsWith/R.endsWith` now support lists as inputs. This way, it matches current Ramda behavior. - Remove unused typing for `R.chain`. - `R.map`/`R.filter` no longer accept bad inputs as iterable. This way, Rambda behaves more like Ramda, which also throws. - Make `R.lastIndexOf` follow the logic of `R.indexOf`. - Change `R.type` logic to Ramda logic. This way, `R.type` can return `Error` and `Set` as results. - Add missing logic in `R.equals` to compare sets - [Issue #599](https://github.com/selfrefactor/rambda/issues/599) - Improve list cloning - [Issue #595](https://github.com/selfrefactor/rambda/issues/595) - Handle multiple inputs with `R.allPass` and `R.anyPass` - [Issue #604](https://github.com/selfrefactor/rambda/issues/604) - Fix `R.length` wrong logic with inputs as `{length: 123}` - [Issue #606](https://github.com/selfrefactor/rambda/issues/606). - Improve non-curry typings of `R.merge` by using types from [mobily/ts-belt](https://github.com/mobily/ts-belt). - Improve performance of `R.uniqWith`. - Wrong `R.update` if index is `-1` - [PR #593](https://github.com/selfrefactor/rambda/pull/593) - Make `R.eqProps` safe for falsy inputs - based on [this opened Ramda PR](https://github.com/ramda/ramda/pull/2943). - Incorrect benchmarks for `R.pipe/R.compose` - [Issue #608](https://github.com/selfrefactor/rambda/issues/608) - Fix `R.last/R.head` typings - [Issue #609](https://github.com/selfrefactor/rambda/issues/609) 6.9.0 - Fix slow `R.uniq` methods - [Issue #581](https://github.com/selfrefactor/rambda/issues/581) Fixing `R.uniq` was done by improving `R.indexOf` which has performance implication to all methods importing `R.indexOf`: - R.includes - R.intersection - R.difference - R.excludes - R.symmetricDifference - R.union - R.without no longer support the following case - `without('0:1', ['0', '0:1']) // => ['0']`. Now it throws as the first argument should be a list, not a string. Ramda, on the other hand, returns an empty list - https://github.com/ramda/ramda/issues/3086. 6.8.3 - Fix Typescript build process with `rambda/immutable` - [Issue #572](https://github.com/selfrefactor/rambda/issues/572) - Add `R.objOf` method - Add `R.mapObjIndexed` method - Publish shorter README.md version to NPM 6.8.0 - `R.has` use `Object.prototype.hasOwnProperty`- [Issue #572](https://github.com/selfrefactor/rambda/issues/572) - Expose `immutable.ts` typings which are Rambda typings with `readonly` statements - [Issue #565](https://github.com/selfrefactor/rambda/issues/565) - Fix `R.intersection` wrong order compared to Ramda. - `R.path` wrong return of `null` instead of `undefined` when path value is `null` - [PR #577](https://github.com/selfrefactor/rambda/pull/577) 6.7.0 - Remove `ts-toolbelt` types from Typescript definitions. Most affected are the following methods, which lose one of its curried definitions: 1. R.maxBy 2. R.minBy 3. R.pathEq 4. R.viewOr 5. R.when 6. R.merge 7. R.mergeDeepRight 8. R.mergeLeft 6.6.0 - Change `R.piped` typings to mimic that of `R.pipe`. Main difference is that `R.pipe` is focused on unary functions. - Fix wrong logic when `R.without` use `R.includes` while it should use array version of `R.includes`. - Use uglify plugin for UMD bundle. - Remove `dist` folder from `.gitignore` in order to fix `Deno` broken package. [Issue #570](https://github.com/selfrefactor/rambda/issues/570) - Improve `R.fromPairs` typings - [Issue #567](https://github.com/selfrefactor/rambda/issues/567) 6.5.3 - Wrong logic where `R.without` use `R.includes` while it should use the array version of `R.includes` This is Ramda bug, that Rambda also has before this release - https://github.com/ramda/ramda/issues/3086 6.5.2 - Wrong `R.defaultTo` typings - changes introduced in v6.5.0 are missing their TS equivalent. - Update dependencies 6.5.1 Fix wrong versions in changelog 6.5.0 - `R.defaultTo` no longer accepts infinite inputs, thus it follows Ramda implementation. - `R.equals` supports equality of functions. - `R.pipe` doesn't use `R.compose`. - Close [Issue #561](https://github.com/selfrefactor/rambda/issues/561) - export several internal TS interfaces and types - Close [Issue #559](https://github.com/selfrefactor/rambda/issues/559) - improve `R.propOr` typings - Add `CHANGELOG.md` file in release files list > This is only part of the changelog. You can read the full text in [CHANGELOG.md](CHANGELOG.md) file. [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#-changelog) ## ❯ Additional info > Most influential contributors - [@farwayer](https://github.com/farwayer) - improving performance in R.find, R.filter; give the idea how to make benchmarks more reliable; - [@thejohnfreeman](https://github.com/thejohnfreeman) - add R.assoc, R.chain; - [@helmuthdu](https://github.com/helmuthdu) - add R.clone; help improve code style; - [@jpgorman](https://github.com/jpgorman) - add R.zip, R.reject, R.without, R.addIndex; - [@ku8ar](https://github.com/ku8ar) - add R.slice, R.propOr, R.identical, R.propIs and several math related methods; introduce the idea to display missing Ramda methods; - [@romgrk](https://github.com/romgrk) - add R.groupBy, R.indexBy, R.findLast, R.findLastIndex; - [@squidfunk](https://github.com/squidfunk) - add R.assocPath, R.symmetricDifference, R.difference, R.intersperse; - [@synthet1c](https://github.com/synthet1c) - add all lenses methods; add R.applySpec, R.converge; - [@vlad-zhukov](https://github.com/vlad-zhukov) - help with configuring Rollup, Babel; change export file to use ES module exports; > Rambda references - [Interview with Dejan Totef at SurviveJS blog](https://survivejs.com/blog/rambda-interview/) - [Awesome functional Javascript programming libraries](https://github.com/stoeffel/awesome-fp-js#libraries) - [Overview of Rambda pros/cons](https://mobily.github.io/ts-belt/docs/#rambda-%EF%B8%8F) > Links to Rambda - [https://mailchi.mp/webtoolsweekly/web-tools-280](Web Tools Weekly) - [https://github.com/stoeffel/awesome-fp-js](awesome-fp-js) - [https://github.com/docsifyjs/awesome-docsify](awesome-docsify) > Deprecated from `Used by` section - [SAP's Cloud SDK](https://github.com/SAP/cloud-sdk) - This repo doesn't uses `Rambda` since *October/2020* [commit that removes Rambda](https://github.com/SAP/cloud-sdk/commit/b29b4f915c4e4e9c2441e7b6b67cf83dac1fdac3) > Releases [Rambda's releases](https://github.com/selfrefactor/rambda/releases) before **6.4.0** were used mostly for testing purposes. [![---------------](https://raw.githubusercontent.com/selfrefactor/rambda/master/files/separator.png)](#-additional-info) ## My other libraries

Niketa theme
Collection of 9 light VSCode themes
Niketa dark theme
Collection of 9 dark VSCode themes
String-fn
String utility library
Useful Javascript libraries
Large collection of JavaScript,Typescript and Angular related repos links
Run-fn
CLI commands for lint JS/TS files, commit git changes and upgrade of dependencies

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