it-parallel

it-parallel

Takes an (async) iterable that emits promise-returning functions, invokes them in parallel up to the concurrency limit and emits the results as they become available, optionally in the same order as the input

Install

$ npm install --save it-parallel

Usage

const parallel = require('it-parallel')
const all = require('it-all')
const delay = require('delay')

// This can also be an iterator, async iterator, generator, etc
const input = [
  async () => {
    console.info('start 1')
    await delay(500)

    console.info('end 1')
    return 1
  },
  async () => {
    console.info('start 2')
    await delay(200)

    console.info('end 2')
    return 2
  },
  async () => {
    console.info('start 3')
    await delay(100)

    console.info('end 3')
    return 3
  }
]

const result = await all(parallel(input, {
  concurrency: 2
}))

// output:
// start 1
// start 2
// end 2
// start 3
// end 3
// end 1

console.info(result) // [2, 3, 1]

If order is important, pass ordered: true as an option:

const result = await all(parallel(input, {
  concurrency: 2,
  ordered: true
}))

// output:
// start 1
// start 2
// end 2
// start 3
// end 3
// end 1

console.info(result) // [1, 2, 3]