iterator-util

Some useful iterator utilities

Usage

resolve

Force value to be a iterable

import {resolve} from 'iterator-util'

const iterable = ['foo', 'bar']
const nonIterable = 'baz'

for (let elem of resolve(iterable)) {
  console.lot(elem)
}

for (let elem of resolve(nonIterable)) {
  console.log(elem)
}

// result: foo bar baz

map

Array#map but lazy as iterator

import {map} from 'iterator-util'

const iterable = [1, 2, 3]

for (let elem of map(iterable, num => num ** 2)) {
  console.log(elem)
}

// result: 1 4 9

concat

Array#concat but lazy as iterator

import {concat} from 'iterator-util'

const head = [1, 2, 3]
const tail = [4, 5, 6]

for (let elem of concat(head, tail)) {
  console.log(elem)
}

// result: 1 2 3 4 5 6

product

Provide cartesian product with given iterables

import {product} from 'iterator-util'

const xCoord = [1, 2, 3]
const yCoord = [1, 2]

for (let [x, y] of product(xCoord, yCoord)) {
  console.log(`(${x}, ${y})`)
}

// result: (1, 1) (1, 2) (2, 1) (2, 2) (3, 1) (3, 2)

indexed

Provide index number to yielded value

import {indexed} from 'iterator-util'

const data = ['foo', 'bar', 'baz']

for (let {index, value} of indexed(data)) {
  console.log(`(${index}, ${value})`)
}

// result: (0, foo) (1, bar) (2, baz)

some

Array#some but lazy as iterator

import {some} from 'iterator-util'

const data = [3, 4, 5]

some(data, d => d > 4) // true
some(data, d => d > 5) // false

every

Array#every but lazy as iterator

import {every} from 'iterator-util'

const data = [3, 4, 5]

every(data, d => d < 5) // false
every(data, d => d < 6) // true

group

Iterate groups with given length

import {group} from 'iterator-util'

const data = [3, 4, 5, 6, 7, 8, 9]

for (let elem of group(data, 3)) {
  console.log(elem)
}

// result: [3, 4, 5] [6, 7, 8] [9, null, null]

take

Take first n elements

import {take} from 'iterator-util'

const data = [3, 4, 5]

take(indexed(data), 2) // [{index: 0, value: 3}, {index: 1, value: 4}]