Web Workers

Web Workers are a way to do threading in JavaScript. It is a simple mean to run work in the background to keep the main thread responsive for UI work.

To use web workers with WMR you can use the Web Workers API directly.

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

// Subscribe to messages coming from the worker
worker.addEventListener('message', e => console.log(e.data));

// Ping worker
worker.postMessage("Let's go");

WMR relies on the filename to detect workers. That's why it must have the .worker suffix in the filename.

// my.worker.js
addEventListener('message', () => {
    // Always answer with "hello"
    postMessage('hello');
});

We highly recommend using comlink for working with web workers. It abstracts away the manual message passing that's required to communicate workers.

# ESM Support in Web Workers

Support for module mode so that you can use import and export statements can be turned on by passing { format: 'module' } to the Worker constructor.

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

Be cautious: ESM is not yet supported in every mainstream browser.