run-parallel

What is run-parallel?

The run-parallel npm package is designed to run multiple functions in parallel, without waiting until the previous function has completed. It is particularly useful for executing asynchronous tasks concurrently, such as I/O operations, in an efficient manner. Once all tasks have completed, a final callback is called with the results of each task.

What are run-parallel's main functionalities?

Running multiple asynchronous tasks in parallel

This feature allows for executing multiple asynchronous tasks concurrently. The code sample demonstrates how to use run-parallel to execute two tasks in parallel, each completing at different times but being processed together.

const runParallel = require('run-parallel')

const tasks = [
  function(callback) {
    setTimeout(function() {
      callback(null, 'one')
    }, 200)
  },
  function(callback) {
    setTimeout(function() {
      callback(null, 'two')
    }, 100)
  }
]

runParallel(tasks, function(err, results) {
  console.log(results) // ['one', 'two']
})

Other packages similar to run-parallel

async

The async package offers a wide range of functions for working with asynchronous JavaScript, including parallel execution. Compared to run-parallel, async provides a broader set of utilities for handling asynchronous operations, making it more versatile but potentially heavier for projects only needing parallel execution.

p-map

p-map is a promise-based map function designed for running multiple promises in parallel, with support for concurrency limits. Unlike run-parallel, which uses callbacks, p-map utilizes promises, making it a better fit for modern asynchronous patterns in JavaScript.

paralleljs

ParallelJS is a library for parallel programming with JavaScript, allowing for the execution of code in parallel processes. It differs from run-parallel by focusing on parallel computation rather than just asynchronous task execution, potentially offering more power for CPU-bound tasks.

README

run-parallel

Run an array of functions in parallel

install

npm install run-parallel

usage

parallel(tasks, [callback])

Run the tasks array of functions in parallel, without waiting until the previous function has completed. If any of the functions pass an error to its callback, the main callback is immediately called with the value of the error. Once the tasks have completed, the results are passed to the final callback as an array.

It is also possible to use an object instead of an array. Each property will be run as a function and the results will be passed to the final callback as an object instead of an array. This can be a more readable way of handling the results.

arguments

• tasks - An array or object containing functions to run. Each function is passed a callback(err, result) which it must call on completion with an error err (which can be null) and an optional result value.
• callback(err, results) - An optional callback to run once all the functions have completed. This function gets a results array (or object) containing all the result arguments passed to the task callbacks.

example

var parallel = require('run-parallel')

parallel([
  function (callback) {
    setTimeout(function () {
      callback(null, 'one')
    }, 200)
  },
  function (callback) {
    setTimeout(function () {
      callback(null, 'two')
    }, 100)
  }
],
// optional callback
function (err, results) {
  // the results array will equal ['one','two'] even though
  // the second function had a shorter timeout.
})

This module is basically equavalent to async.parallel, but it's handy to just have the one function you need instead of the kitchen sink. Modularity! Especially handy if you're serving to the browser and need to reduce your javascript bundle size.

Works great in the browser with browserify!

see also

• run-auto
• run-parallel-limit
• run-series
• run-waterfall

license

MIT. Copyright (c) Feross Aboukhadijeh.