promisify-worker

A lightweight simple promisification interface for web workers. Allows you to dispatch messages with worker.postMessage and receive the answer as a promise.

Install with npm i -S promisify-worker.

Demo: https://andrewghc.github.io/promisify-worker/

Example

This example uses Webpack's worker-loader.

Main thread

import promisifyWorker from 'promisify-worker';
import Worker from './your-web-worker-path';

async function doSomething(worker) {
  const answer = await worker.postMessage({ command: 'hello' });
  console.log(answer);
}

const worker = promisifyWorker(new Worker());
doSomething(worker);

Worker thread

self.addEventListener('message', ({ data: { command, messageId } }) => {
  switch (command) {
    case 'hello':
      self.postMessage({ message: 'hi there', messageId });
      break;
    default:
      self.postMessage({ message: 'this shouldn\'t happen!', messageId });
  }
});

Use

The exported function promisifyWorker accepts two arguments:

promifyWorker(worker[, namespace = 'messageId']).

worker: A web worker.

namespace: A namespace used to identify events. Defaults to messageId.

For this library to work, the worker thread must include the namespace when calling postMessage. This also means that worker threads must respond with an object. Please see the example for this in practice.

Important notes

This library uses and does not transpile Proxies, these are available in all modern browsers.