miazzy / worker-loader

A webpack loader that registers a script as a Web Worker

worker-loader

worker loader module for webpack

Getting Started

To begin, you'll need to install worker-loader:

$ npm install worker-loader --save-dev

Inlined

App.js

import Worker from 'worker-loader!./Worker.js';

Config

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.js$/,
        use: { loader: 'worker-loader' },
      },
    ],
  },
};

App.js

import Worker from './file.worker.js';

const worker = new Worker();

worker.postMessage({ a: 1 });
worker.onmessage = function (event) {};

worker.addEventListener('message', function (event) {});

And run webpack via your preferred method.

Options

fallback

Type: Boolean Default: false

Require a fallback for non-worker supporting environments.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.js$/,
        use: { loader: 'worker-loader' },
        options: { fallback: true },
      },
    ],
  },
};

inline

Type: Boolean Default: false

You can also inline the worker as a BLOB with the inline parameter.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.js$/,
        use: { loader: 'worker-loader' },
        options: { inline: true },
      },
    ],
  },
};

Note: Inline mode will also create chunks for browsers without support for inline workers, to disable this behavior just set fallback parameter as false.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        loader: 'worker-loader',
        options: { inline: true, fallback: false },
      },
    ],
  },
};

name

Type: String Default: [hash].worker.js

To set a custom name for the output script, use the name parameter. The name may contain the string [hash], which will be replaced with a content dependent hash for caching purposes. When using name alone [hash] is omitted.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        loader: 'worker-loader',
        options: { name: 'WorkerName.[hash].js' },
      },
    ],
  },
};

publicPath

Type: String Default: null

Overrides the path from which worker scripts are downloaded. If not specified, the same public path used for other webpack assets is used.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        loader: 'worker-loader',
        options: { publicPath: '/scripts/workers/' },
      },
    ],
  },
};

workerType

Type: string Default: Worker

Set the worker type. Defaults to Worker. Supports ServiceWorker, SharedWorker.

Examples

Basic

The worker file can import dependencies just like any other file:

Worker.js

const _ = require('lodash');

const obj = { foo: 'foo' };

_.has(obj, 'foo');

// Post data to parent thread
self.postMessage({ foo: 'foo' });

// Respond to message from parent thread
self.addEventListener('message', (event) => console.log(event));

Integrating with ES Modules

Note: You can even use ES2015 Modules if you have the babel-loader configured.

Worker.js

import _ from 'lodash';

const obj = { foo: 'foo' };

_.has(obj, 'foo');

// Post data to parent thread
self.postMessage({ foo: 'foo' });

// Respond to message from parent thread
self.addEventListener('message', (event) => console.log(event));

Integrating with TypeScript

To integrate with TypeScript, you will need to define a custom module for the exports of your worker

typings/worker-loader.d.ts

declare module 'worker-loader!*' {
  class WebpackWorker extends Worker {
    constructor();
  }

  export default WebpackWorker;
}

Worker.ts

const ctx: Worker = self as any;

// Post data to parent thread
ctx.postMessage({ foo: 'foo' });

// Respond to message from parent thread
ctx.addEventListener('message', (event) => console.log(event));

App.ts

import Worker from 'worker-loader!./Worker';

const worker = new Worker();

worker.postMessage({ a: 1 });
worker.onmessage = (event) => {};

worker.addEventListener('message', (event) => {});

Cross-Origin Policy

WebWorkers are restricted by a same-origin policy, so if your webpack assets are not being served from the same origin as your application, their download may be blocked by your browser. This scenario can commonly occur if you are hosting your assets under a CDN domain. Even downloads from the webpack-dev-server could be blocked. There are two workarounds:

Firstly, you can inline the worker as a blob instead of downloading it as an external script via the inline parameter

App.js

import Worker from './file.worker.js';

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        loader: 'worker-loader',
        options: { inline: true },
      },
    ],
  },
};

Secondly, you may override the base download URL for your worker script via the publicPath option

App.js

// This will cause the worker to be downloaded from `/workers/file.worker.js`
import Worker from './file.worker.js';

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        loader: 'worker-loader',
        options: { publicPath: '/workers/' },
      },
    ],
  },
};

Contributing

Please take a moment to read our contributing guidelines if you haven't yet done so.

CONTRIBUTING

License

MIT