rambdax

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

it("when returns true", () => {
  const numArr = [ 0, 1, 2, 3, 4 ]
  const fn = val => val > -1
  expect(R.all(fn, numArr)).toBeTruthy()
})

allPass

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

both

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

compact

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

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)
})

either

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

flip

flip(fn: Function): Function

It returns copy of the function fn with exchanged order of the first and second function arguments.

const fn = (a,b) => a - b
const flipped = R.flip(fn)
fn(4,1)      // =>  3 
flipped(4,1) // => -3

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]

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.

race

race(promised: Object): Object

It acts as Promise.race for object with promises.

const delay = ms => new Promise(resolve => {
  setTimeout(() => {
    resolve(ms)
  }, ms)
})
const promises = {
  a : delay(20),
  b : delay(10),
}

R.race(promises)
.then(result =>{
  // => { a: 10 }
})

const delay = ms => new Promise((resolve,reject) => {
  setTimeout(() => {
    reject(ms)
  }, ms)
})
const promises = {
  a : delay(1),
  b : delay(2),
}
R.race(promises)
.then(console.log)
.catch(err =>{
  // => { a: 1 }
})

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
}

resolveObj

resolveObj(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"

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

---

Methods inherited from Rambda

add

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

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

adjust

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

• Replaces i index in arr with the result of replaceFn(arr[i])

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

any

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

• 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']

compose

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

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]

contains

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

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

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

Returns defaultArgument if inputArgument is undefined or the type of inputArgument is different of the type of defaultArgument.

Returns inputArgument in any other case.

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

drop

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

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

Returns arrOrStr with howManyToDrop items dropped from the right

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

equals

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

• Returns equality match between a and b

Doesn't handles cyclical data structures

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

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

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

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 ]

has

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

• 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

• Returns the first element of arrOrStr

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

indexOf

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

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

• 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

• Returns the last element of arrOrStr

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

length

length(arrOrStr: Array|String): Number

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

map

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

Returns the result of looping through arr with mapFn

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

match

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

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

merge

merge(a: Object, b: Object)

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

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

omit

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

• 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

• 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

• 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(valueToPrepend: any, arr: Array): Array

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

prop

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

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

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

• 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

• 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'

sort

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

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

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']

subtract

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

Returns a minus b

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

tail

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

• 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

• 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

• 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'

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('s') //=> "String"
R.type(1) //=> "Number"
R.type(false) //=> "Boolean"
R.type(null) //=> "Null"
R.type(/[A-z]/) //=> "RegExp"

uniq

uniq(arr: Array): Array

• 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

• 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

• Returns array with of all values in obj

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