Introduction

Web Workers are great for moving long blocking work and large modules off the main thread, keeping UI updates fast and smooth. In many cases, code running in a worker will need to rely on some of the same modules as code used on the main thread or in other workers.

The Test

This test checks to see if it's possible to share modules between Web Workers and the main thread, or between multiple workers. Since few browsers support ECMAScript modules in workers, a custom module format or runtime module loader is necessary in order to pass this test.

index.js

import workerURL from 'get-worker-url-somehow';
import { logCaps } from './utils.js';

new Worker(workerURL);
logCaps('This is index');

worker.js

import { logCaps } from './utils.js';
logCaps('This is worker');

utils.js

export function logCaps(msg) {
  console.log(msg.toUpperCase());
}

The result should be three scripts: one for the main thread containing index.js, one for the worker containing worker.js, and one for the dependencies shared by both (logCaps()). As with other bundle URL tests, the worker's URL must be hashed.