markdown-body entry-content container-lg" itemprop="text">

worker-loader

DEPRECATED for v5: https://webpack.js.org/guides/web-workers/

Web Worker loader for webpack 4.

Note that this is specific to webpack 4. To use Web Workers in webpack 5, see https://webpack.js.org/guides/web-workers/.

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

Name	Type	Default	Description
`worker`	`{String\|Object}`	`Worker`	Allows to set web worker constructor name and options
`publicPath`	`{String\|Function}`	based on `output.publicPath`	specifies the public URL address of the output files when referenced in a browser
`filename`	`{String\|Function}`	based on `output.filename`	The filename of entry chunks for web workers
`chunkFilename`	`{String}`	based on `output.chunkFilename`	The filename of non-entry chunks for web workers
`inline`	`'no-fallback'\|'fallback'`	`undefined`	Allow to inline the worker as a `BLOB`
`esModule`	`{Boolean}`	`true`	Use ES modules syntax

`worker`

Type: String|Object Default: Worker

Set the worker type.

`String`

Allows to set web worker constructor name.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.(c|m)?js$/i,
        loader: "worker-loader",
        options: {
          worker: "SharedWorker",
        },
      },
    ],
  },
};

`Object`

Allow to set web worker constructor name and options.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.(c|m)?js$/i,
        loader: "worker-loader",
        options: {
          worker: {
            type: "SharedWorker",
            options: {
              type: "classic",
              credentials: "omit",
              name: "my-custom-worker-name",
            },
          },
        },
      },
    ],
  },
};

`publicPath`

Type: String|Function Default: based on output.publicPath

The publicPath specifies the public URL address of the output files when referenced in a browser. If not specified, the same public path used for other webpack assets is used.

`String`

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.(c|m)?js$/i,
        loader: "worker-loader",
        options: {
          publicPath: "/scripts/workers/",
        },
      },
    ],
  },
};

`Function`

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.(c|m)?js$/i,
        loader: "worker-loader",
        options: {
          publicPath: (pathData, assetInfo) => {
            return `/scripts/${pathData.hash}/workers/`;
          },
        },
      },
    ],
  },
};

`filename`

Type: String|Function Default: based on output.filename, adding worker suffix, for example - output.filename: '[name].js' value of this option will be [name].worker.js

The filename of entry chunks for web workers.

`String`

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.(c|m)?js$/i,
        loader: "worker-loader",
        options: {
          filename: "[name].[contenthash].worker.js",
        },
      },
    ],
  },
};

`Function`

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.(c|m)?js$/i,
        loader: "worker-loader",
        options: {
          filename: (pathData) => {
            if (
              /\.worker\.(c|m)?js$/i.test(pathData.chunk.entryModule.resource)
            ) {
              return "[name].custom.worker.js";
            }

            return "[name].js";
          },
        },
      },
    ],
  },
};

`chunkFilename`

Type: String Default: based on output.chunkFilename, adding worker suffix, for example - output.chunkFilename: '[id].js' value of this option will be [id].worker.js

The filename of non-entry chunks for web workers.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.(c|m)?js$/i,
        loader: "worker-loader",
        options: {
          chunkFilename: "[id].[contenthash].worker.js",
        },
      },
    ],
  },
};

`inline`

Type: 'fallback' | 'no-fallback' Default: undefined

Allow to inline the worker as a BLOB.

Inline mode with the fallback value will create file for browsers without support web workers, to disable this behavior just use no-fallback value.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.(c|m)?js$/i,
        loader: "worker-loader",
        options: {
          inline: "fallback",
        },
      },
    ],
  },
};

`esModule`

Type: Boolean Default: true

By default, worker-loader generates JS modules that use the ES modules syntax.

You can enable a CommonJS modules syntax using:

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.(c|m)?js$/i,
        loader: "worker-loader",
        options: {
          esModule: false,
        },
      },
    ],
  },
};

Examples

Basic

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

index.js

import Worker from "./my.worker.js";

var worker = new Worker();

var result;

worker.onmessage = function (event) {
  if (!result) {
    result = document.createElement("div");
    result.setAttribute("id", "result");

    document.body.append(result);
  }

  result.innerText = JSON.stringify(event.data);
};

const button = document.getElementById("button");

button.addEventListener("click", function () {
  worker.postMessage({ postMessage: true });
});

my.worker.js

onmessage = function (event) {
  var workerResult = event.data;

  workerResult.onmessage = true;

  postMessage(workerResult);
};

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.(c|m)?js$/i,
        loader: "worker-loader",
        options: {
          esModule: false,
        },
      },
    ],
  },
};

Integrating with ES6+ features

You can even use ES6+ features if you have the babel-loader configured.

index.js

import Worker from "./my.worker.js";

const worker = new Worker();

let result;

worker.onmessage = (event) => {
  if (!result) {
    result = document.createElement("div");
    result.setAttribute("id", "result");

    document.body.append(result);
  }

  result.innerText = JSON.stringify(event.data);
};

const button = document.getElementById("button");

button.addEventListener("click", () => {
  worker.postMessage({ postMessage: true });
});

my.worker.js

onmessage = function (event) {
  const workerResult = event.data;

  workerResult.onmessage = true;

  postMessage(workerResult);
};

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.worker\.(c|m)?js$/i,
        use: [
          {
            loader: "worker-loader",
          },
          {
            loader: "babel-loader",
            options: {
              presets: ["@babel/preset-env"],
            },
          },
        ],
      },
    ],
  },
};

Integrating with TypeScript

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

Loading with `worker-loader!`

typings/worker-loader.d.ts

declare module "worker-loader!*" {
  // You need to change `Worker`, if you specified a different value for the `workerType` option
  class WebpackWorker extends Worker {
    constructor();
  }

  // Uncomment this if you set the `esModule` option to `false`
  // export = WebpackWorker;
  export default WebpackWorker;
}

my.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));

index.ts

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

const worker = new Worker();

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

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

Loading without `worker-loader!`

Alternatively, you can omit the worker-loader! prefix passed to import statement by using the following notation. This is useful for executing the code using a non-WebPack runtime environment (such as Jest with workerloader-jest-transformer).

typings/worker-loader.d.ts

declare module "*.worker.ts" {
  // You need to change `Worker`, if you specified a different value for the `workerType` option
  class WebpackWorker extends Worker {
    constructor();
  }

  // Uncomment this if you set the `esModule` option to `false`
  // export = WebpackWorker;
  export default WebpackWorker;
}

my.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));

index.ts

import MyWorker from "./my.worker.ts";

const worker = new MyWorker();

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

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

webpack.config.js

module.exports = {
  module: {
    rules: [
      // Place this *before* the `ts-loader`.
      {
        test: /\.worker\.ts$/,
        loader: "worker-loader",
      },
      {
        test: /\.ts$/,
        loader: "ts-loader",
      },
    ],
  },
  resolve: {
    extensions: [".ts", ".js"],
  },
};

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: "fallback" },
      },
    ],
  },
};

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

worker-loader

Getting Started

Inlined

Config

Options

worker

String

Object

publicPath

String

Function

filename

String

Function

chunkFilename

inline

esModule

Examples

Basic

Integrating with ES6+ features

Integrating with TypeScript

Loading with worker-loader!

Loading without worker-loader!

Cross-Origin Policy

Contributing

License

`worker`

`String`

`Object`

`publicPath`

`String`

`Function`

`filename`

`String`

`Function`

`chunkFilename`

`inline`

`esModule`

Loading with `worker-loader!`

Loading without `worker-loader!`

Uh oh!

License

webpack-contrib/worker-loader

ErrorLooks like something went wrong!

About

Topics

Resources

License

Uh oh!

Stars

Watchers

Forks

Releases 13

Sponsor this project

Uh oh!

Packages 0

Used by 73k

Contributors 41

Uh oh!

Languages

Error
Looks like something went wrong!

Packages