Rambdax

Extended version of Rambda(utility library) - Documentation

Simple example

const R = require("rambdax")
const result = R.compose(
  R.filter(val => val>2),
  R.flatten,
)([ [1], [2], [3], 4])
console.log(result) // => [3,4]

How to use it?

Simple npm i rambdax is sufficient

Differences between Rambda and Ramda

• Rambda's equals doesn't protect against circular structures as Ramda.equals does

• Rambda's map/filter works only for arrays, while Ramda's map/filter accept also objects

• Rambda's type detect async functions. The returned value is "Async"

Differences between Rambda and Ramdax

Rambdax passthrough all Rambda's methods and introduce some new functions.

The idea of Rambdax is to extend Rambda without worring for Ramda compatibility.

API

API part I - Rambdax own methods

all

all(fn: Function, arr: Array): Boolean

It returns true if all members of array arr returns true, when applied as argument to function fn.

const numArr = [ 0, 1, 2, 3, 4 ]
const fn = x => x > -1
expect(R.all(fn, numArr)).toBeTruthy()

allPass

allPass(rules: Array, input: any): Boolean

It returns true if all functions of rules return true, when input is their argument.

const obj = {
  a : 1,
  b : 2,
}
const conditionArr = [
  val => val.a === 1,
  val => val.b === 2,
]
expect(
  R.allPass(conditionArr, obj)
).toBeTruthy()

both

both(x: Function, y: Function, input: any): Boolean

It returns true if both function x and function y return true, when input is their argument.

const fn = R.both(
  a => a > 10,
  a => a < 20
)
fn(15) //=> true
fn(30) //=> false

compact

compact(arr: Array)

It removes the empty values from an array arr.

const arr = [
  1,
  null,
  undefined,
  false,
  "",
  " ",
  "foo", {},
  [],
  [1],
  /\s/g
]
const result = R.compact(arr)
const expectedResult = [1, false, " ", "foo", [1]]
expect(result).toEqual(expectedResult)

composeAsync

composeAsync(fn1: Function|Async, .. , fnN: Function|Async)(startValue: any): Promise

• compose that accepts async functions as arguments

const delayAsync = async ms => delay(ms)

const delay = ms => new Promise(resolve=>{
  setTimeout(function () {
    resolve(ms+110)
  }, ms)
})

const result = await composeAsync(
  a => a - 1000,
  a => a,
  async a => delayAsync(a),
  a => a+11
)(await delay(20))
expect(
  result
).toEqual(-749)

debounce

debounce(fn: Function, wait: Number): any

it("", async() => {
  let counter = 0
  const inc = () => {
    counter++
  }

  const delay = ms => new Promise(resolve => {
    setTimeout(resolve, ms)
  })
  const incWrapped = debounce(inc, 500)
  incWrapped()
  expect(counter).toBe(0)
  await delay(200)
  incWrapped()
  expect(counter).toBe(0)
  await delay(200)
  incWrapped()
  expect(counter).toBe(0)
  await delay(200)
  incWrapped()
  expect(counter).toBe(0)
  await delay(700)
  expect(counter).toBe(1)
})

delay

delay(ms: Number): Promise<R.DELAY>

setTimeout as a promise that resolves toR.DELAY variable.

R.delay(1000).then( result => {
  console.assert( result === R.DELAY )
})

either

either(x: Function, y: Function, input: any): Boolean

It returns true if one of x(input) and y(input) returns true.

const fn = R.either(
  a => a > 10,
  a => a % 2 === 0
)
fn(15) //=> true
fn(6) //=> true
fn(7) //=> false

evolve

evolve (rules: Object, input: Object): Object

Properties of input object are transformed according to rules object that contains functions as values.

If property prop of rules is a function and also a property of input, then input[prop] will be equal to the result of rules[prop](input[prop]).

rules[prop] can be also a object that contains functions, as you can see in the example below:

const input = {
    firstName : "  Tomato ",
    data      : {
      elapsed   : 100,
      remaining : 1400,
    },
    id : 123,
  }
const rules = {
    firstName : R.trim,
    lastName  : R.trim, //Will not get invoked.
    data      : {
      elapsed   : R.add(1),
      remaining : R.add(-1),
    },
  }

const result = R.evolve(transformations, tomato)
expect(result).toEqual({
  firstName: "Tomato",
  data: {
    elapsed: 101,
    remaining: 1399,
  },
  id: 123,
})

intersection

intersection(a: Array, b: Array): Array

It returns array with the overlapped members of a and b.

R.intersection([1,2,3,4], [7,6,5,4,3]); //=> [4, 3]

isType

isType(xType: string, x: any): Boolean

It returns true if R.type of x is equal to xType.

isArray

isArray(x: any): Boolean

isString

isString(x: any): Boolean

isObject

isObject(x: any): Boolean

isPromiseLike

isPromiseLike(x: any): Boolean

isValid

isValid(input: Object, schema: Object): Boolean

It checks if input is following schema specifications.

This is full copy of json-validity library.

const songSchema = {
  published: "number",
  style: [ "rock", "jazz" ],
  title: "string",
}

const song = {
  published: 1975,
  style: "rock",
  title: "In my time of dying",
}

R.isValid(song,songSchema) // => true

mapAsync

mapAsync(fn: Async|Promise, arr: Array): Promise

Sequential asynchronous mapping with fn over members of arr

const fn = a => new Promise(resolve => {
  setTimeout(() => {
    resolve(a + 100)
  }, 100)
})

const result = await R.composeAsync(
  R.mapAsync(async a => await fn(a)),
  R.mapAsync(fn),
  R.map(a => a * 10)
)([1, 2, 3])
expect(result).toEqual([210, 220, 230])

mapFastAsync

mapAsync(fn: Async|Promise, arr: Array): Promise

Parrallel asynchronous mapping with fn over members of arr

const fn = a => new Promise(resolve => {
  setTimeout(() => {
    resolve(a + 100)
  }, 100)
})

const result = await R.composeAsync(
  R.mapAsync(async a => await fn(a)),
  R.mapAsync(fn),
  R.map(a => a * 10)
)([1, 2, 3])
expect(result).toEqual([210, 220, 230])

memoize

memoize(fn: Function|Promise): any

When fn is called for a second time with the same input, then the cache result is returned instead of calling fn.

describe("memoize", () => {
  it("normal function", () => {
    let counter = 0
    const fn = (a,b) =>{
      counter++
      return a+b
    }
    const memoized = R.memoize(fn)
    expect(memoized(1,2)).toBe(3)
    expect(memoized(1,2)).toBe(3)
    expect(memoized(1,2)).toBe(3)
    expect(counter).toBe(1)
    expect(memoized(2,2)).toBe(4)
    expect(counter).toBe(2)
    expect(memoized(1,2)).toBe(3)
    expect(counter).toBe(2)
  })

  it("async function", async () => {
    let counter = 0
    const delay = ms => new Promise(resolve => {
      setTimeout(resolve, ms)
    })
    const fn = async (ms,a,b) => {
      await delay(ms)
      counter++
      return a+b
    }

    const memoized = R.memoize(fn)
    expect(await memoized(100,1,2)).toBe(3)
    expect(await memoized(100,1,2)).toBe(3)
    expect(await memoized(100,1,2)).toBe(3)
    expect(counter).toBe(1)
    expect(await memoized(100,2,2)).toBe(4)
    expect(counter).toBe(2)
    expect(await memoized(100,1,2)).toBe(3)
    expect(counter).toBe(2)
  })
})

mergeAll

mergeAll(input: Array): Object

It merges all objects of input array sequentially and returns the result.

const arr = [
  {a:1},
  {b:2},
  {c:3}
]
const expectedResult = {
  a:1,
  b:2,
  c:3
}
expect(R.mergeAll(arr)).toEqual(expectedResult)

omitBy

omitBy(fn: function, input: Object): Object

It returns only those properties of input that return false when passed to fn.

const input = {
  a: 1,
  b: 2,
  c: 3,
  d: 4,
}
const fn = (prop, val) => val < 3
const expectedResult = {
  c: 3,
  d: 4,
}
expect(R.omitBy(fn, input)).toEqual(expectedResult)

once

once(fn: Function): Function

It returns a function, which invokes only oncefn.

const addOneOnce = R.once((a, b, c) => a + b + c)

expect(addOneOnce(10,20,30)).toBe(60)
expect(addOneOnce(40)).toEqual(60)

pickBy

pickBy(fn: Function, input: Object): Object

It returns only those properties of input that return true when passed to fn.

const input = {
  a: 1,
  b: 2,
  c: 3,
  d: 4,
}
const fn = (prop,val) => val > 3 || prop === 'a'
const expectedResult = {
  a: 1,
  d: 4,
}
expect(R.pickBy(fn, input)).toEqual(expectedResult)

produce

produce( conditions: Object, input: any): Promise|Object

const conditions = {
  foo: a => a > 10,
  bar: a => ({baz:a})
}

const result = R.produce(conditions, 7)

const expectedResult = {
  foo: false,
  bar: {baz: 7}
}
result === expectedResult // => true

conditions is an object with sync or async functions as values.

The values of the returned object returnValue are the results of those functions when input is passed. The properties of the returned object are equal to input.

If any of the conditions is a Promise, then the returned value is a Promise that resolves to returnValue.

random

random(min: Number, max: Number)

It returns a random number between min inclusive and max inclusive.

const randomResult = R.random(1, 10)
expect(randomResult).toBeLessThanOrEqual(10)
expect(randomResult).toBeGreaterThanOrEqual(1)

rangeBy

rangeBy(start: Number, end: Number, step: Number)

It returns array of all numbers between start and end, when the step of increase is step.

expect(
  R.rangeBy(0, 10, 2)
).toEqual([0, 2, 4, 6, 8, 10])
expect(
  R.rangeBy(0, 2, 0.3)
).toEqual([0, 0.3, 0.6, 0.9, 1.2, 1.5, 1.8])

renameProps

Typing:

R.renameProps(rules: Object, input: Object): Object

If property prop of rules is also a property in input, then rename input property to rules[prop].

Example:

const rules = {
  f: "foo",
  b: "bar"
}
const input = {
  f:1,
  b:2
}
const result = R.renameProps(rules, input)
const expectedResult = {
  foo:1,
  bar:2
}

resolve

resolve(promises: Object): Object

It acts as Promise.all for object with Promises.

const delay = ms => new Promise(resolve => {
  setTimeout(() => {
    resolve(ms)
  }, ms)
})
const promises = {
  a : delay(1),
  b : delay(2),
  c : delay(3),
}
const result = await R.resolveObj(promises)
// => { a:1, b:2, c:3 }

resolveSecure

resolveObj(promises: Array): Array<{type: 'result'|'error', payload:any}>

It acts as Promise.all with fault tollerance.

Error err in any of the promises would simply add {type: 'error', payload: err} to the returned array. Result result in any of the promises adds {type: 'result', payload: result}.

const delay = ms => new Promise(res => {
  setTimeout(() => res(ms), ms)
})

const fail = async ms => {
  try {
    JSON.parse("{:a")
  }
  catch (err) {
    throw new Error(err)
  }
}

const arr = [delay(2000), fail(1000), delay(1000)]
const result = await R.resolveSecure(arr)
const expectedResult = [
  {
    "payload": 2000,
    "type": "result"
  },
  {
    payload:"Unexpected token : in JSON at position 1",
    type: "error"
  },
  {
    "payload": 2000,
    "type": "result"
  }
]
// => result === expectedResult

shuffle

shuffle(arr: Array): Array

It returns randomized copy of arr.

tap

tap(fn: Function, inputArgument: T): T

It returns back inputArgument after calling fn with inputArgument.

const log = a => console.log(a)
const result = R.tap(log, "foo")
// the console logs `foo`
// `result` is equal to "foo"

tapAsync

tapAsync(fn: Function|Async|Promise, inputArgument: T): T

It is R.tap that accept promise-like fn argument.

const log = async a => {
  await R.delay(1000)
  console.log(a)
}
const result = R.tapAsync(log, "foo")
// the console logs `foo`
// `result` is equal to "foo"

throttle

throttle(fn: Function, period: Number): Function

It creates a throttled function that invokes fn maximum once for a period of milliseconds.

let counter = 0
const inc = () => {
  counter++
}

const delay = ms => new Promise(resolve => {
  setTimeout(resolve, ms)
})
const incWrapped = throttle(inc, 1000)
await delay(500)
incWrapped()
incWrapped()
incWrapped()
expect(counter).toBe(1)
await delay(1500)
incWrapped()
expect(counter).toBe(2)

where

where(conditions: Object, input: Object): Boolean

Each property prop in conditions is a function.

This function is called with input(prop). If all such function calls return true, then the final result is also true.

const condition = R.where({
  a : aProp => typeof aProp === "string",
  b : bProp => bProp === 4
})

condition({
  a : "foo",
  b : 4,
  c : 11,
}) //=> true

condition({
  a : 1,
  b : 4,
  c : 11,
}) //=> false

wrap

wrap({fn: Function, when: Function|Async, defaultTo: any}): Promise|Function

It returns a function or a Promise with input argument input.

• When fn is called with input, then intermediateResult is obtained.

• fn can be from the asynchronous entity, i.e. Promise or Async

• if that is the case, when can also be a Promise-like

• when is called with intermediateResult to obtain whenResult.

• If whenResult is true, then the final result is defaultTo.

• If whenResult is false, then the final result is intermediateResult.

const result = R.wrap({
  fn: R.filter(a => a > 3),
  defaultTo:  [ 4 ],
  when:       x => R.length(x) === 0
})([1, 2, 3])

expect(result)
.toEqual([4])

when

when(rule: Function, fn: Function): Function

var truncate = R.when( x => x.length > 5, R.compose(x =>${x}...`, R.take(5)) )

expect(truncate('1234')).toEqual('1234') expect(truncate('12345678')).toEqual('12345...') `

Methods inherited from Rambda

add

add(a: Number, b: Number): Number

R.add(2, 3) // =>  5

addIndex

addIndex(fn: Function): Function

const mapWithIndex = R.addIndex(R.map)
mapWithIndex(
  (val, index) => `${val} - ${index}`,
  ["A", "B", "C"]
) // => ["A - 0", "B - 1", "C - 2"]

adjust

adjust(replaceFn: Function, i:Number, arr:Array): Array

It replaces i index in arr with the result of replaceFn(arr[i]).

R.adjust(a => a + 1, 0, [0, 100]) // => [1, 100]

all

all(fn: Function, arr: Array): Boolean

It returns true if all members of array arr returns true, when applied as argument to function fn.

const arr = [ 0, 1, 2, 3, 4 ]
const fn = x => x > -1
R.all(fn, arr) // => true

allPass

allPass(rules: Array, input: any): Boolean

It returns true if all functions of rules return true, when input is their argument.

const input = {
  a : 1,
  b : 2,
}
const rules = [
  x => x.a === 1,
  x => x.b === 2,
]
R.allPass(conditionArr, obj) // => true

always

always(x: any): Function

It returns function that always returns x.

const fn = R.always(7)

fn()// => 7
fn()// => 7

any

any(condition: Function, arr: Array): Boolean

It returns true if at least one member of arr returns true, when passed to the condition function.

R.any(a => a * a > 8)([1, 2, 3]) // => true
R.any(a => a * a > 10)([1, 2, 3]) // => false

append

append(valueToAppend: any, arr: Array): Array

R.append('foo', ['bar', 'baz']) // => ['foo', 'bar', 'baz']

both

both(x: Function, y: Function, input: any): Boolean

It returns true if both function x and function y return true, when input is their argument.

const fn = R.both(
  a => a > 10,
  a => a < 20
)
fn(15) //=> true
fn(30) //=> false

compose

compose(fn1: Function, ... , fnN: Function): any

It performs right-to-left function composition.

const result = R.compose(
  R.map(a => a*2)
  R.filter(val => val>2),
)([1, 2, 3, 4])
console.log(result) // => [6, 8]

complement

complement(fn: Function): Function

It returns complemented function that accept input as argument.

The return value of complemented is the negative boolean value of fn(input).

R.complement(R.always(0)) // => true
R.complement(R.always(true)) // => false

concat

concat(x: Array|String, y: Array|String): Array|String

It returns new string or array, which is result merging x and y.

R.concat([1, 2])([3, 4]) // => [1, 2, 3, 4]
R.concat('foo', 'bar') // => 'foobar'

contains

contains(valueToFind: any, arr: Array): Boolean

It returns true if valueToFind is part of arr.

R.contains(2, [1, 2]) // => true
R.contains(3, [1, 2]) // => false

curry

curry(fn: Function): Function

It returns curried version of fn.

const addFourNumbers = (a, b, c, d) => a + b + c + d
const curriedAddFourNumbers = R.curry(addFourNumbers)
const f = curriedAddFourNumbers(1, 2)
const g = f(3)
g(4) // => 10

defaultTo

defaultTo(defaultArgument: T, inputArgument: any): T

It returns defaultArgument if inputArgument is undefined or the type of inputArgument is different of the type of defaultArgument.

It returns inputArgument in any other case.

R.defaultTo('foo', undefined) // => 'foo'
R.defaultTo('foo')('bar') // => 'bar'
R.defaultTo('foo')(1) // => 'foo'

divide

R.divide(71, 100) // => 0.71

drop

drop(howManyToDrop: Number, arrOrStr: Array|String): Array|String

It returns arrOrStr with howManyToDrop items dropped from the left.

R.drop(1, ['foo', 'bar', 'baz']) // => ['bar', 'baz']
R.drop(1, 'foo')  // => 'oo'

dropLast

dropLast(howManyToDrop: Number, arrOrStr: Array|String): Array|String

It returns arrOrStr with howManyToDrop items dropped from the right.

R.dropLast(1, ['foo', 'bar', 'baz']) // => ['foo', 'bar']
R.dropLast(1, 'foo')  // => 'fo'

endsWith

endsWith(x: any, arrOrStr: Array|String): Boolean

R.endsWith(
  'bar',
  "foo-bar"
) // => true

R.endsWith(
  'baz',
  "foo-bar"
) // => false

either

const fn = R.either(
  a => a > 10,
  a => a % 2 === 0
)
fn(15) //=> true
fn(6) //=> true
fn(7) //=> false

equals

equals(a: any, b: any): Boolean

It returns equality match between a and b.

It doesn't handle cyclical data structures.

R.equals(1, 1) // => true
R.equals({}, {}) // => false
R.equals([1, 2, 3], [1, 2, 3]) // => true

F

R.F() // => false

filter

filter(filterFn: Function, arr: Array): Array

Filters arr throw boolean returning filterFn

const filterFn = a => a % 2 === 0

R.filter(filterFn, [1, 2, 3, 4]) // => [2, 4]

find

find(findFn: Function, arr: Array): T|undefined

It returns undefined or the first element of arr satisfying findFn.

const findFn = a => R.type(a.foo) === "Number"
const arr = [{foo: "bar"}, {foo: 1}]
R.find(findFn, arr) // => {foo: 1}

findIndex

findIndex(findFn: Function, arr: Array): Number

It returns -1 or the index of the first element of arr satisfying findFn.

const findFn = a => R.type(a.foo) === "Number"
const arr = [{foo: "bar"}, {foo: 1}]
R.find(findFn, arr) // => 1

flatten

flatten(arr: Array): Array

R.flatten([ 1, [ 2, [ 3 ] ] ])
// => [ 1, 2, 3 ]

flip

flip(fn: Function): Function

It returns function which calls fn with exchanged first and second argument.

const subtractFlip = R.flip(R.subtract)
R.subtractFlip(1,7)
// => 6

Note that it works only for functions that expects two arguments. If third argument is passed, then undefined is returned.

has

has(prop: String, obj: Object): Boolean

• It returns true if obj has property prop.

R.has("a", {a: 1}) // => true
R.has("b", {a: 1}) // => false

head

head(arrOrStr: Array|String): any

It returns the first element of arrOrStr.

R.head([1, 2, 3]) // => 1
R.head('foo') // => 'f'

identity

identity(x: T): T

It just passes back the supplied arguments.

R.identity(7) // => 7

ifElse

ifElse(condition: Function, ifFn: Function, elseFn: Function): Function

It returns function, which expect input as argument and returns finalResult.

When the function is called, a value answer is generated as a result of condition(input).

If answer is true, then finalResult is equal to ifFn(input). If answer is false, then finalResult is equal to elseFn(input).

const fn = R.ifElse(
 x => x > 10,
 x => x*2,
 x => x*10
)
fn(8) // => 80
fn(11) // => 22

indexOf

indexOf(valueToFind: any, arr: Array): Number

It returns -1 or the index of the first element of arr equal of valueToFind.

R.indexOf(1, [1, 2]) // => 0

init

init(arrOrStr: Array|String): Array|String

• It returns all but the last element of arrOrStr.

R.init([1, 2, 3])  // => [1, 2]
R.init('foo')  // => 'fo'

join

join(separator: String, arr: Array): String

R.join('-', [1, 2, 3])  // => '1-2-3'

last

last(arrOrStr: Array|String): any

• It returns the last element of arrOrStr.

R.last(['foo', 'bar', 'baz']) // => 'baz'
R.last('foo') // => 'o'

lastIndexOf

lastIndexOf(x: any, arr: Array): Number

R.lastIndexOf(1, [1, 2, 3, 1, 2]) // => 3
R.lastIndexOf(10, [1, 2, 3, 1, 2]) // => -1

length

length(arrOrStr: Array|String): Number

R.length([1, 2, 3]) // => 3

map

map(mapFn: Function, arr: Array): Array

It returns the result of looping through arr with mapFn.

const mapFn = x => x * 2;
R.map(mapFn, [1, 2, 3]) // => [2, 4, 6]

match

match(regExpression: Regex, str: String): Array

R.match(/([a-z]a)/g, 'bananas') // => ['ba', 'na', 'na']

merge

merge(a: Object, b: Object)

It returns result of Object.assign({}, a, b).

R.merge({ 'foo': 0, 'bar': 1 }, { 'foo': 7 })
// => { 'foo': 7, 'bar': 1 }

modulo

modulo(a: Number, b: Number): Number

It returns the remainder of operation a/b.

R.module(14,3) // => 2

multiply

multiply(a: Number, b: Number): Number

It returns the result of operation a*b.

R.module(14,3) // => 2

not

not(x: any): Boolean

It returns inverted boolean version of input x.

R.not(true); //=> false
R.not(false); //=> true
R.not(0); //=> true
R.not(1); //=> false

omit

omit(propsToOmit: Array, obj: Object): Object

It returns a partial copy of an obj with omitting propsToOmit

R.omit(['a', 'd'], {a: 1, b: 2, c: 3}) // => {b: 2, c: 3}

path

path(pathToSearch: Array|String, obj: Object): any

Retrieve the value at pathToSearch in object obj

R.path('a.b', {a: {b: 2}}) // => 2
R.path(['a', 'b'], {a: {b: 2}}) // => 2
R.path(['a', 'c'], {a: {b: 2}}) // => undefined

partialCurry

partialCurry(fn: Function|Async, a: Object, b: Object): Function|Promise

When called with function fn and first set of input a, it will return a function.

This function will wait to be called with second set of input b and it will invoke fn with the merged object of a over b.

fn can be asynchronous function. In that case a Promise holding the result of fn is returned.

See the example below:

const fn = ({a, b, c}) => {
  return (a * b) + c
}
const curried = R.partialCurry(fn, {a: 2})
curried({b: 3, c: 10}) // => 16

• Note that partialCurry is method specific for Rambda and the method is not part of Ramda's API

• You can read my argumentation for creating partialCurry here

pick

pick(propsToPick: Array, obj: Object): Object

It returns a partial copy of an obj containing only propsToPick properties.

R.pick(['a', 'c'], {a: 1, b: 2}) // => {a: 1}

pluck

pluck(property: String, arr: Array): Array

It returns list of the values of property taken from the objects in array of objects arr.

R.pluck('a')([{a: 1}, {a: 2}, {b: 3}]) // => [1, 2]

prepend

prepend(x: any, arr: Array): Array

It adds x to the start of the array arr.

R.prepend('foo', ['bar', 'baz']) // => ['foo', 'bar', 'baz']

prop

prop(propToFind: String, obj: Object): any

It returns undefined or the value of property propToFind in obj

R.prop('x', {x: 100}) // => 100
R.prop('x', {a: 1}) // => undefined

propEq

propEq(propToFind: String, valueToMatch: any, obj: Object): Boolean

It returns true if obj has property propToFind and its value is equal to valueToMatch

const propToFind = "foo"
const valueToMatch = 0
R.propEq(propToFind, valueToMatch)({foo: 0}) // => true
R.propEq(propToFind, valueToMatch)({foo: 1}) // => false

range

range(start: Number, end: Number): Array

It returns a array of numbers from start(inclusive) to end(exclusive).

R.range(0, 2)   // => [0, 1]

reduce

reduce(iteratorFn: Function, accumulator: any, array: Array): any

It returns a single item by iterating through the list, successively calling the iterator function iteratorFn and passing it an accumulator value and the current value from the array, and then passing the result to the next call.

The iterator function behaves like the native callback of the Array.prototype.reduce method.

const iteratorFn = (acc, val) => acc + val
R.reduce(iteratorFn, 1, [1, 2, 3])   // => 7

repeat

repeat(valueToRepeat: T, num: Number): Array

R.repeat('foo', 2) // => ['foo', 'foo']

replace

replace(strOrRegex: String|Regex, replacer: String, str: String): String

Replace strOrRegex found in str with replacer

R.replace('foo', 'bar', 'foo foo') // => 'bar foo'
R.replace(/foo/, 'bar', 'foo foo') // => 'bar foo'
R.replace(/foo/g, 'bar', 'foo foo') // => 'bar bar'

reverse

!!! It modifies the array instead of returning new copy, as original Ramda method does.

const arr = [1, 2]
R.reverse(arr)
console.log(arr) // => [2, 1]

sort

sort(sortFn: Function, arr: Array): Array

It returns copy of arr sorted by sortFn.

sortFn must return Number

const sortFn = (a, b) => a - b
R.sort(sortFn, [3, 1, 2]) // => [1, 2, 3]

sortBy

sortBy(sortFn: Function, arr: Array): Array

It returns copy of arr sorted by sortFn.

sortFn must return value for comparison

const sortFn = obj => obj.foo
R.sortBy(sortFn, [
  {foo: 1},
  {foo: 0}
])
// => [{foo: 0}, {foo: 1}]

split

split(separator: String, str: String): Array

R.split('-', 'a-b-c') // => ['a', 'b', 'c']

splitEvery

splitEvery(sliceLength: Number, arrOrString: Array|String): Array

• Splits arrOrStr into slices of sliceLength

R.splitEvery(2, [1, 2, 3]) // => [[1, 2], [3]]
R.splitEvery(3, 'foobar') // => ['foo', 'bar']

startsWith

startsWith(x: any, arrOrStr: Array|String): Boolean

R.endsWith(
  'bar',
  "foo-bar"
) // => true

R.endsWith(
  'baz',
  "foo-bar"
) // => false

subtract

subtract(a: Number, b: Number): Number

R.subtract(3, 1) // => 2

T

R.T() // => true

tail

tail(arrOrStr: Array|String): Array|String

• It returns all but the first element of arrOrStr

R.tail([1, 2, 3])  // => [2, 3]
R.tail('foo')  // => 'oo'

take

take(num: Number, arrOrStr: Array|String): Array|String

• It returns the first num elements of arrOrStr.

R.take(1, ['foo', 'bar']) // => ['foo']
R.take(2, ['foo']) // => 'fo'

takeLast

takeLast(num: Number, arrOrStr: Array|String): Array|String

• It returns the last num elements of arrOrStr.

R.takeLast(1, ['foo', 'bar']) // => ['bar']
R.takeLast(2, ['foo']) // => 'oo'

test

test(regExpression: Regex, str: String): Boolean

• Determines whether str matches regExpression

R.test(/^f/, 'foo') // => true
R.test(/^f/, 'bar') // => false

toLower

toLower(str: String): String

R.toLower('FOO') // => 'foo'

toString

toString(x: any): String

R.toString([1, 2]) // => '1,2'

toUpper

toUpper(str: String): String

R.toUpper('foo') // => 'FOO'

trim

trim(str: String): String

R.trim('  foo  ') // => 'foo'

type

type(a: any): String

R.type(() => {}) // => "Function"
R.type(async () => {}) // => "Async"
R.type([]) // => "Array"
R.type({}) // => "Object"
R.type('foo') // => "String"
R.type(1) // => "Number"
R.type(true) // => "Boolean"
R.type(null) // => "Null"
R.type(/[A-z]/) // => "RegExp"

const delay = ms => new Promise(resolve => {
  setTimeout(function () {
    resolve()
  }, ms)
})
R.type(delay) // => "Promise"

uniq

uniq(arr: Array): Array

It returns a new array containing only one copy of each element in arr.

R.uniq([1, 1, 2, 1]) // => [1, 2]
R.uniq([1, '1'])     // => [1, '1']

update

update(i: Number, replaceValue: any, arr: Array): Array

It returns a new copy of the arr with the element at i index replaced with replaceValue.

R.update(0, "foo", ['bar', 'baz']) // => ['foo', baz]

values

values(obj: Object): Array

It returns array with of all values in obj.

R.values({a: 1, b: 2}) // => [1, 2]

includes

includes(x: any, arrOrStr: Array|String): Boolean

R.includes(1, [1, 2]) // => true
R.includes('oo', 'foo') // => true
R.includes('z', 'foo') // => false

Note that this method is not part of Ramda API.

padEnd

padEnd(x: Number, str: String): String

R.padEnd(3, 'foo') // => 'foo '

Note that this method is not part of Ramda API.

padStart

padStart(x: Number, str: String): String

R.padStart(3, 'foo') // => ' foo'

Note that this method is not part of Ramda API.