Small JavaScript library that helps run inline functions in Web Workers.
Switch branches/tags
Nothing to show
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.

Inline Worker

Inline Worker is a small JavaScript library that helps run inline functions in Web Workers.

Web Workers allow you to run long-running scripts without blocking UI and other scripts because they run in a different thread. However, this requires that the code will be contained in a separate file. Thanks to other newly defined native HTML5 objects like Blob and URL it is possible to run inline functions in Web Workers.

Haven't heard about Web Workers yet? Check out some tutorials on MDN and HTML5 Rocks.


More examples can be found in the test directory.

Simple inline worker

// Define worker with inline function
var inlineWorker = new InlineWorker(function (num) {
	return num * num;

// Do something with the result
inlineWorker.then(function (value) {
	console.log(value); // => 25

// Start worker;

// Each method is chainable. You can run it in this way:
	.then(function (value) { console.log(value); })

Injecting functions

function cube(n) {
	return n * n;

function sqrt(num) {
	return Math.sqrt(num);

const NUM = 5;

// Define worker
var inlineWorker = new InlineWorker(function (num) {
	return sqrt(cube(num));

// Remember to inject functions used in a callback passed to the InlineWorker constructor.
// In other case they will not be found because the callback is serialized
// when passing to the worker. Moreover, these functions must be named functions.
inlineWorker.inject(cube, sqrt);

// Do something with the result
inlineWorker.then(function (val) {
	console.log(val); // => NUM

// Start worker;



InlineWorker(callback(arg: any): function)

Constructor which creates an inline worker instance using provided callback. It's lazy i.e. Web Worker is created later when necessary.

  • callback(arg: any) - arg is an argument passed to the worker when calling run method.


then ([success(value: any): function], [error(value: ErrorEvent): function])

Using then method, success and error callbacks can be passed to the Web Worker. Both are optional.

  • success(value: any) is called each time the worker posts message. value is a data property of event object.
  • error(value: ErrorEvent) is called if any error occures inside the worker.
run (data: any, [transfer: Array<Transferable>])

Passes data to the worker. Arguments are passed as they are to the native postMessage method.

  • data can be any data (primitive values, structured data) except DOM objects and other objects that cannot be cloned.
  • transfer is an optional argument which can be used to send ArrayBuffer objects efficiently i.e. transfering them rather than cloning them.
inject (...fns: function | fns: Array<function>)

This method injects functions to the worker.

  • fns can be a variable length list of function references or an array of function references.


  • it should be possible to pass callback and required functions in this way new InlineWorker([sqrt, cube], function () {...}),
  • implement addEventListener (alias on) method to handle multiple listeners on success and error,
  • implement MapReduce algorithm.

Similar projects

  • parallel.js is a similar library which makes parallel computing in JavaScript easier.