iterable-operator

iterable-operator

Utilities for JavaScript Iterable and AsyncIterable.

Install

npm install --save iterable-operator
# or
yarn add iterable-operator

Usage

import { map, toArray } from 'iterable-operator'

const iter = [1, 2, 3]
const doubleIter = map(iter, x => x * 2)
const result = toArray(doubleIter)

Chaining

import { IterableOperator } from 'iterable-operator/lib/es2018/style/chaining'

const result = new IterableOperator([1, 2, 3])
  .map(x => x * 2)
  .toArray()

Binding

It is prepared for bind-operator.

import { map, toArray } from 'iterable-operator/lib/es2018/style/binding'

const result = [1, 2, 3]
  ::map(x => x * 2)
  ::toArray()

Pipeline

It is prepared for pipeline-operator.

import { map, toArray } from 'iterable-operator/lib/es2018/style/pipeline'

const result = [1, 2, 3]
  |> map(x => x * 2)
  |> toArray()

API

There are two kinds of operators:

• Intermediate operation(middleware): lazy, the first parameter is Iterable, the return value is Iterable(Iterable in, Iterable out)
• Terminal operation(output): the first parameter is Iterable

Middleware

chunk, chunkAsync

function chunk<T>(iterable: Iterable<T>, size: number): Iterable<T[]>
function chunkAsync<T>(iterable: AsyncIterable<T>, size: number): AsyncIterable<T[]>
// size > 0

chunk([1, 2, 3], 2) // [[1, 2], [3]]
chunk([1, 2, 3], 3) // [[1, 2, 3]]
chunk([1, 2, 3], 5) // [[1, 2, 3]]
chunk([1, 2, 3], 0) // throw Error
chunk([1, 2, 3], -1) // throw Error

The memory usage of this function depends on size.

chunkBy, chunkByAsync

function chunkBy<T>(
  iterable: Iterable<T>
, predicate: (element: T, index: number) => unknown
): Iterable<T[]>
function chunkByAsync<T>(
  iterable: Iterable<T> | AsyncIterable<T>
, predicate: (element: T, index: number) => unknown | PromiseLike<unknown>
): AsyncIterable<T[]>

chunkBy([1, 2, 3], x => x === 2) // [[1, 2], [3]]
chunkBy([1, 2, 3], x => x === 3) // [[1, 2, 3]]
chunkBy([1, 2, 3], x => x === 5) // [[1, 2, 3]]

The memory usage of this function depends on iterable and predicate.

concat, concatAsync

function concat<T, U>(
  iterable: Iterable<T>
, ...otherIterables: Iterable<U>[]
): Iterable<T | U> {
function concatAsync<T, U>(
  iterable: Iterable<T | PromiseLike<T>> | AsyncIterable<T>
, ...otherIterables: Array<Iterable<U | PromiseLike<U>> | AsyncIterable<U>>
): AsyncIterable<T | U> {

concat([1, 2, 3]) // [1, 2, 3]
concat([1, 2, 3], ['a', 'b', 'c']) // [1, 2, 3, 'a', 'b', 'c']

drop, dropAsync

function drop<T>(iterable: Iterable<T>, count: number): Iterable<T>
function dropAsync<T>(iterable: AsyncIterable<T>, count: number): AsyncIterable<T>
// count >= 0

drop([1, 2, 3], 0) // [1, 2, 3]
drop([1, 2, 3], 2) // [3]
drop([1, 2, 3], 3) // []
drop([1, 2, 3], 5) // []
drop([1, 2, 3], -1) // throw Error

dropRight, dropRightAsync

function dropRight<T>(iterable: Iterable<T>, count: number): Iterable<T>
function dropRightAsync<T>(iterable: AsyncIterable<T>, count: number): AsyncIterable<T>
// count >= 0

dropRight([1, 2, 3], 0) // [1, 2, 3]
dropRight([1, 2, 3], 2) // [1]
dropRight([1, 2, 3], 3) // []
dropRight([1, 2, 3], 5) // []
dropRight([1, 2, 3], -1) // throw Error

The memory usage of this function depends on iterable.

dropUntil, dropUntilAsync

function dropUntil<T>(
  iterable: Iterable<T>
, predicate: (element: T, index: number) => unknown
): Iterable<T>
function dropUntilAsync<T>(
  iterable: Iterable<T> | AsyncIterable<T>
, predicate: (element: T, index: number) => boolean | PromiseLike<boolean>
): AsyncIterable<T>

dropUntil([1, 2, 3], x => x === 2) // [2, 3]

The memory usage of this function depends on iterable and predicate.

filter, filterAsync

function filter<T, U extends T = T>(
  iterable: Iterable<T>
, predicate: (element: T, index: number) => unknown
): Iterable<U>
function filterAsync<T, U extends T = T>(
  iterable: Iterable<T> | AsyncIterable<T>
, predicate: (element: T, index: number) => unknown | PromiseLike<unknown>
): AsyncIterable<U>

filter([1, 2, 3], x => x % 2 === 1) // [1, 3]

flatten, flattenAsync

function flatten<T>(iterable: Iterable<unknown>): Iterable<T>
function flattenAsync<T>(iterable: AsyncIterable<unknown>): AsyncIterable<T>

flatten([]) // []
flatten('123') // ['1', '2', '3']
flatten(['one', ['two'], 0, [1, [2]]]) // ['o', 'n', 'e', 'two', 0, 1, [2]]

flattenDeep, flattenDeepAsync

function flattenDeep<T>(iterable: Iterable<unknown>, depth: number = Infinity): Iterable<T>
function flattenDeepAsync<T>(
  iterable: AsyncIterable<unknown>
, depth: number = Infinity
): AsyncIterable<T>
// depth >= 0

flattenDeep([]) // []
flattenDeep('123') // ['1', '2', '3']
flattenDeep([], -1) // throw Error
flattenDeep([0, [1]], 0) // [0, [1]]
flattenDeep(['one', ['two', ['three']], 0, [1, [2, [3]]]], 2) // ['o', 'n', 'e', 't', 'w', 'o', 'three', 0, 1, 2, [3]]

flattenBy, flattenByAsync

function flattenBy<T>(
  iterable: Iterable<unknown>
, predicate: (element: unknown, level: number) => boolean
): Iterable<T>
function flattenByAsync<T>(
  iterable: Iterable<unknown> | AsyncIterable<unknown>
, predicate: (element: unknown, level: number) => boolean | PromiseLike<unknown>
): AsyncIterable<T>

flattenBy(['one', ['two'], 0, [1]], x => typeof x !== 'string') // ['one', 'two', 0, 1]
flattenBy([], () => true) // []
flattenBy('123', () => true) // ['1', '2', '3']

map, mapAsync

function map<T, U>(
  iterable: Iterable<T>
, fn: (element: T, index: number) => U
): Iterable<U>
function mapAsync<T, U>(
  iterable: Iterable<T> | AsyncIterable<T>
, fn: (element: T, index: number) => U | PromiseLike<U>
): AsyncIterable<U>

map([1, 2, 3], x => x * 2) // [2, 4, 6]

repeat, repeatAsync

function repeat<T>(iterable: Iterable<T>, times: number): Iterable<T>
function repeatAsync<T>(iterable: AsyncIterable<T>, times: number): AsyncIterable<T>
// times >= 0

repeat([1, 2, 3], 2) // [1, 2, 3, 1, 2, 3]
repeat([1, 2, 3], 0) // []
repeat([1, 2, 3], -1) // throw Error

The memory usage of this function depends on iterable.

slice, sliceAsync

function slice<T>(
  iterable: Iterable<T>
, start: number
, end: number = Infinity
): Iterable<T>
function sliceAsync<T>(
  iterable: AsyncIterable<T>
, start: number
, end: number = Infinity
): AsyncIterable<T>
// start >= 0, end >= start

slice([1, 2, 3], -1, 1) // throw Error
slice([1, 2, 3], 3, 5) // []
slice([1, 2, 3], 1, 2) // [2]
slice([1, 2, 3], 1, 1) // []
slice([1, 2, 3], 2, 1) // throw Error

split, splitAsync

function split<T>(iterable: Iterable<T>, separator: T): Iterable<T[]>
function splitAsync<T>(iterable: AsyncIterable<T>, separator: T): AsyncIterable<T[]>

split([1, 2, 3, 4, 5], 3) // [[1, 2], [4, 5]]
split([1, 2, 3, 4, 5], 1) // [[], [2, 3, 4, 5]]
split([1, 2, 3, 4, 5], 5) // [[1, 2, 3, 4], []]
split([1, 2, 3, 4, 5], 0) // [[1, 2, 3, 4, 5]]

The memory usage of this function depends on iterable and separator.

splitBy, splitByAsync

function splitBy<T>(
  iterable: Iterable<T>
, predicate: (element: T, index: number) => unknown
): Iterable<T[]>
function splitByAsync<T>(
  iterable: Iterable<T> | AsyncIterable<T>
, predicate: (element: T, index: number) => unknown | PromiseLike<unknown>
): AsyncIterable<T[]>

splitBy([1, 2, 3, 4, 5], x => x === 3) // [[1, 2], [4, 5]]
splitBy([1, 2, 3, 4, 5], x => x === 1) // [[], [2, 3, 4, 5]]
splitBy([1, 2, 3, 4, 5], x => x === 5) // [[1, 2, 3, 4], []]
splitBy([1, 2, 3, 4, 5], x => x === 0) // [[1, 2, 3, 4, 5]]

The memory usage of this function depends on iterable and predicate.

take, takeAsync

function take<T>(iterable: Iterable<T>, count: number): Iterable<T>
function takeAsync<T>(iterable: AsyncIterable<T>, count: number): AsyncIterable<T>

take([1, 2, 3], 5) // [1, 2, 3]
take([1, 2, 3], 2) // [1, 2]
take([1, 2, 3], 0) // []
take([1, 2, 3], -1) // throw Error

takeRight, takeRightAsync

function takeRight<T>(iterable: Iterable<T>, count: number): Iterable<T>
function takeRightAsync<T>(iterable: AsyncIterable<T>, count: number): AsyncIterable<T>

takeRight([1, 2, 3], 2) // [2, 3]
takeRight([1, 2, 3], 5) // [1, 2, 3]
takeRight([1, 2, 3], 0) // []
takeRight([1, 2, 3], -1) // throw Error

The memory usage of this function depends on count.

takeUntil, takeUntilAsync

function takeUntil<T>(
  iterable: Iterable<T>
, predicate: (element: T, index: number) => unknown
): Iterable<T>
function takeUntilAsync<T>(
  iterable: Iterable<T> | AsyncIterable<T>
, predicate: (element: T, index: number) => unknown | PromiseLike<unknown>
): AsyncIterable<T>

takeUntil([1, 2, 3], x => x === 2) // [1]

tap, tapAsync

function tap<T>(
  iterable: Iterable<T>
, fn: (element: T, index: number) => unknown
): Iterable<T> {
function tapAsync<T>(
  iterable: Iterable<T> | AsyncIterable<T>
, fn: (element: T, index: number) => unknown | PromiseLike<unknown>
): AsyncIterable<T>

tap([1, 2, 3], x => console.log(x)) // [1, 2, 3]

toAsyncIterable

function toAsyncIterable<T>(iterable: Iterable<T | PromiseLike<T>>): AsyncIterable<T>

toAsyncIterable([1, 2, 3]) // AsyncIterable [1, 2, 3]

transform, transformAsync

function transform<T, U>(
  iterable: Iterable<T>
, transformer: (iterable: Iterable<T>) => Iterable<U>
): Iterable<U>
function transformAsync<T, U>(
  iterable: Iterable<T>
, transformer: (iterable: Iterable<T>) => AsyncIterable<U>
): AsyncIterable<U>
function transformAsync<T, U>(
  iterable: AsyncIterable<T>
, transformer: (iterable: AsyncIterable<T>) => AsyncIterable<U>
): AsyncIterable<U>

transform([1, 2, 3], function* double(iter) {
  for (const element of iter) {
    yield element * 2
  }
}) // [2, 4, 6]

uniq, uniqAsync

function uniq<T>(iterable: Iterable<T>): Iterable<T>
function uniqAsync<T>(iterable: AsyncIterable<T>): AsyncIterable<T>

uniq([1, 1, 2, 2, 3, 3]) // [1, 2, 3]

The memory usage of this function depends on iterable.

uniqBy, uniqByAsync

function uniqBy<T, U>(
  iterable: Iterable<T>
, fn: (element: T, index: number) => U
): Iterable<T> {
function uniqByAsync<T, U>(
  iterable: Iterable<T> | AsyncIterable<T>
, fn: (element: T, index: number) => U | PromiseLike<U>
): AsyncIterable<T>

uniqBy([1, 2, 3], x => x % 2) // [1, 2]

The memory usage of this function depends on fn.

zip, zipAsync

function zip<T, U extends Array<Iterable<unknown>>>(
  iterable: Iterable<T>
, ...otherIterables: U
): Iterable<[T, ...ExtractTypeTupleFromIterableTuple<U>]> {
function zipAsync<T, U extends Array<Iterable<unknown> | AsyncIterable<unknown>>>(
  iterable: Iterable<T | PromiseLike<T>> | AsyncIterable<T>
, ...otherIterables: U
): AsyncIterable<[T, ...ExtractTypeTupleFromAsyncLikeIterableTuple<U>]> {

zip([1, 2, 3], ['a', 'b', 'c']) // [[1, 'a'], [2, 'b'], [3, 'c']]
zip([1, 2, 3], ['a', 'b']) // [[1, 'a'], [2, 'b']
zip([1, 2, 3], ['a', 'b'], ['i', 'ii', 'iii']) // [[1, 'a', 'i'], [2, 'b', 'ii']]

Output

consume

function consume<T, U>(iterable: Iterable<T>, consumer: (iterable: Iterable<T>) => U): U
function consume<T, U>(
  iterable: AsyncIterable<T>
, consumer: (iterable: AsyncIterable<T>) => U
): U

consume([1, 2, 3], xs => new Set(xs)) // Set [1, 2, 3]

each, eachAsync

function each<T>(iterable: Iterable<T>, fn: (element: T, index: number) => unknown): void
function eachAsync<T>(
  iterable: Iterable<T> | AsyncIterable<T>
, fn: (element: T, index: number) => unknown | PromiseLike<unknown>
): Promise<void>

each([1, 2, 3], x => console.log(x)) // void

every, everyAsync

function every<T>(
  iterable: Iterable<T>
, predicate: (element: T, index: number) => unknown
): boolean
function everyAsync<T>(
  iterable: Iterable<T> | AsyncIterable<T>
, predicate: (element: T, index: number) => unknown | PromiseLike<unknown>
): Promise<boolean>

every([1, 2, 3], x => x < 5) // true
every([1, 2, 3], x => x <= 2) // false

find, findAsync

function find<T>(
  iterable: Iterable<T>
, predicate: (element: T, index: number) => unknown
): T | undefined
function findAsync<T>(
  iterable: Iterable<T> | AsyncIterable<T>
, predicate: (element: T, index: number) => unknown | PromiseLike<unknown>
): Promise<T | undefined>

find([1, 2, 3], x => x === 2) // 2
find([1, 2, 3], x => x === 4) // undefined

first, firstAsync

function first<T>(iterable: Iterable<T>): T | undefined
function firstAsync<T>(iterable: AsyncIterable<T>): Promise<T | undefined>

first([1, 2, 3]) // 1
first([]) // undefined

includes, includesAsync

function includes<T>(iterable: Iterable<T>, value: T): boolean
function includesAsync<T>(iterable: AsyncIterable<T>, value: T): Promise<boolean>

includes([1, 2, 3], 2) // true
includes([1, 2, 3], 4) // false

last, lastAsync

function last<T>(iterable: Iterable<T>): T | undefined
function lastAsync<T>(iterable: AsyncIterable<T>): Promise<T | undefined>

last([1, 2, 3]) // 3
last([]) // undefined

match, matchAsync

function match<T>(iterable: Iterable<T>, sequence: ArrayLike<T>): boolean
function matchAsync<T>(
  iterable: AsyncIterable<T>
, sequence: ArrayLike<T>
): Promise<boolean>

match([1, 2, 3], [2, 3]) // true
match([1, 2, 3], [3, 2]) // false
match([1, 2, 3], []) // true

reduce, reduceAsync

function reduce<T, U>(
  iterable: Iterable<T>
, fn:
    ((accumulator: T, currentValue: T, index: number) => T)
  & ((accumulator: U, currentValue: T, index: number) => U)
, initialValue?: U
)
function reduceAsync<T, U>(
  iterable: Iterable<T> | AsyncIterable<T>
, fn:
    ((accumulator: T, currentValue: T, index: number) => T | PromiseLike<T>)
  & ((accumulator: U, currentValue: T, index: number) => U | PromiseLike<U>)
, initialValue?: U
)

reduce([], (acc, cur) => acc + cur) // throw Error
reduce([1], (acc, cur) => acc + cur) // 1
reduce([1, 2, 3], (acc, cur) => acc + cur) // 6

reduce([1, 2, 3], (acc, cur, index) => {
  acc.push([cur, index])
  return acc
}) // [[1, 0], [2, 1], [3, 2]]

some, someAsync

function some<T>(
  iterable: Iterable<T>
, predicate: (element: T, index: number) => unknown
): boolean
function someAsync<T>(
  iterable: Iterable<T> | AsyncIterable<T>
, predicate: (element: T, index: number) => unknown | PromiseLike<unknown>
): Promise<boolean>

some([1, 2, 3], x => x === 2) // true
some([1, 2, 3], x => x === 4) // false

toArray, toArrayAsync

function toArray<T>(iterable: Iterable<T>): T[]
function toArrayAsync<T>(iterable: AsyncIterable<T>): Promise<T[]>

toArray([1, 2, 3]) // Array [1, 2, 3]

toSet, toSetAsync

function toSet<T>(iterable: Iterable<T>): Set<T>
function toSetAsync<T>(iterable: AsyncIterable<T>): Promise<Set<T>>

toSet([1, 1, 2, 2, 3, 3]) // Set [1, 2, 3]