0.1.7 • Public • Published


Inspired heavily by webworkify and webworkify-webpack-dropin

launch a web worker that can require() in the browser with browserify and webpack


First, a main.js file will launch the worker.js and print its output:

var resolveWorker = function() {
  var result;

  try {
    result = require.resolve('./worker.js');
  } catch (e) {}

  return result;

var work = require('webworkify');

var w = work(require('./worker.js'), resolveWorker());
w.addEventListener('message', function (ev) {

w.postMessage(4); // send the worker a message

then worker.js can require() modules of its own.

NOTE: resolveWorker() is used because he module id of the worker is required to pass along with the worker when webpack is used to bundle the project. Webpack will resolve module ids at build time by replacing calls to require.resolve. Browserify does not do this however, and we have to resolve the module ids ourselves using the dependency graph provided by browserify, so the try{}catch{} is added to prevent runtime errors.

The worker function lives inside of the module.exports:

var gamma = require('gamma');

module.exports = function (self) {
    self.addEventListener('message',function (ev){
        var startNum = parseInt(ev.data); // ev.data=4 from main.js

        setInterval(function () {
            var r = startNum / Math.random() - 1;
            self.postMessage([ startNum, r, gamma(r) ]);
        }, 500);

Now after browserifying this example, the console will contain output from the worker:

[ 4, 0.09162078520553618, 10.421030346237066 ]
[ 4, 2.026562457360466, 1.011522336481017 ]
[ 4, 3.1853125018703716, 2.3887589540750214 ]
[ 4, 5.6989969260510005, 72.40768854476167 ]
[ 4, 8.679491643020487, 20427.19357947782 ]
[ 4, 0.8528139834191428, 1.1098187157762498 ]
[ 4, 8.068322137547542, 5785.928308309402 ]


var work = require('webworkify')

var w = work(require(modulePath), moduleId)

Return a new web worker from the module at modulePath.

The file at modulePath should export its worker code in module.exports as a function that will be run with no arguments.

Note that all the code outside of the module.exports function will be run in the main thread too so don't put any computationally intensive code in that part. It is necessary for the main code to require() the worker code to fetch the module reference and load modulePath's dependency graph into the bundle output.

moduleId is required when bundling with webpack. You can get the moduleId by calling require.resolve(modulePath). It is suggested to use a resolveWorker() function like in the above example to avoid runtime errors when bundled with browserify.

var resolveWorker = function() {
  var result;

  try {
    result = require.resolve(modulePath);
  } catch (e) {}

  return result;


The worker w returned by webworkify has the property objectURL attached. w.objectURL refers to the Object URL that was used to pass the module's source to the worker, and can be cleaned up using URL.revokeObjectURL(). (See example)


With npm do:

npm install webwackify






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npm i webwackify

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