web-worker

The web-worker package provides a unified, web-compatible Worker implementation that works identically in both the browser and Node.js.

• In Node.js: It implements the Web Worker API on top of Node's worker_threads.
• In the browser: It acts as an alias for the native Worker API.

This allows you to write worker code once and publish it as an npm module that runs in any environment. It emulates browser-style WorkerGlobalScope within the worker and supports DOM-style events (Event.data, Event.type, etc.) and event handler properties (worker.onmessage = ...).

import Worker from 'web-worker';

const worker = new Worker('data:,postMessage("hello")');
worker.onmessage = e => console.log(e.data);  // "hello"

To load a worker file relative to the current module (especially important in Node.js to avoid issues with process.cwd()), use new URL('./path/to/worker.js', import.meta.url). This ensures the worker path is resolved correctly regardless of the application's base directory.

import Worker from 'web-worker';

const url = new URL('./worker.js', import.meta.url);
const worker = new Worker(url);

worker.addEventListener('message', e => {
  console.log(e.data);
});

worker.postMessage('hello');

// Inside worker.js:
// addEventListener('message', e => {
//   if (e.data === 'hello') {
//     postMessage('hiya!');
//   }
// });

To use ES Modules within a worker, set the type option to 'module' during construction. This allows the worker to use import statements.

Note: If using data: URLs as the worker source with type: 'module', Node.js 12.10+ is required. If not supported, the library will attempt to fall back to a 'classic' worker using evaluateDataUrl.

const worker = new Worker('data:text/javascript,import { func } from "./mod.js"; func();', {
  type: 'module'
});

You can create a worker directly from a string using a Data URL. This works for both classic and module workers.

import Worker from 'web-worker';

const worker = new Worker(`data:application/javascript,postMessage(42)`);
worker.addEventListener('message', e => {
  console.log(e.data);  // 42
});

You can instantiate Module Workers by passing { type: 'module' } in the options object.

• Node.js: Supported in Node 12.8+ using the web-worker plugin, leveraging native ES Modules.
• Browser: Supported natively in Chrome 80+. For other browsers, use worker-plugin or rollup-plugin-off-main-thread.

Usage is identical across environments.

import Worker from 'web-worker';

const worker = new Worker(
  new URL('./worker.mjs', import.meta.url),
  { type: 'module' }
);

worker.addEventListener('message', e => {
  console.log(e.data);
});

worker.postMessage('https://httpstat.us/200');

// Inside worker.mjs:
// import fetch from 'isomorphic-fetch';
// addEventListener('message', async e => {
//   const url = e.data;
//   const res = await fetch(url);
//   const text = await res.text();
//   postMessage(text);
// });

This module provides a safe way to access the native Worker API in browser environments. It exports the global Worker constructor if it is defined in the current environment; otherwise, it returns undefined. This allows for feature detection and prevents runtime errors in environments where Web Workers are not supported.

import Worker from 'web-worker/browser';

if (Worker) {
  const myWorker = new Worker('worker.js');
} else {
  console.log('Web Workers are not supported in this environment.');
}

The web-worker package provides a default export that acts as a constructor for a Worker instance. This allows you to instantiate workers using the standard new Worker(...) pattern, typically used for offloading heavy computations or background tasks in a web environment.

import Worker from 'web-worker';

const myWorker = new Worker('worker-script.js');

The web-worker package provides a web-compatible Worker implementation for Node.js environments. It uses Node's worker_threads under the hood but exposes a DOM-style API.

To use it, import the default export. The module automatically detects if it is running in the main thread or a worker thread and provides the appropriate interface.

Key Features:

• Uses DOM-style events (message, error, close).
• Supports event handler properties like worker.onmessage.
• Accepts a module URL or a data: URL.
• Supports the { type: 'module' } option for Module Workers.

import Worker from 'web-worker';

const worker = new Worker('./worker-script.js', { 
  name: 'my-worker', 
  type: 'module' 
});

worker.onmessage = (event) => {
  console.log('Received:', event.data);
};

worker.postMessage({ hello: 'world' });

worker.terminate();

When instantiating a new Worker, you can pass an optional options object to configure its behavior.

const worker = new Worker(url, {
  name: 'my-worker-name',
  type: 'module'
});