Small and performant API for communicating with Web Workers using Promises.

Goals:

• Tiny footprint (~2.5kB min+gz)
• Assumes you have a separate worker.js file (easier to debug, better browser support)
• JSON.stringifys messages for performance

Install:

npm install promise-worker

Inside your main bundle:

// main.js
var PromiseWorker = require('promise-worker');
var worker = new Worker('worker.js');
var promiseWorker = new PromiseWorker(worker);

promiseWorker.postMessage('ping').then(function (response) {
  // handle response
}).catch(function (error) {
  // handle error
});

Inside your worker.js bundle:

// worker.js
var registerPromiseWorker = require('promise-worker/register');

registerPromiseWorker(function (message) {
  return 'pong';
});

Note that you require() two separate APIs, so the library is split between the worker.js and main file. This keeps the total bundle size smaller.

If you prefer script tags, you can get PromiseWorker via:

<script src="https://npmcdn.com/promise-worker/dist/promise-worker.js"></script>

And inside the worker, you can get registerPromiseWorker via:

importScripts('https://npmcdn.com/promise-worker/dist/promise-worker.register.js');

The message you send can be any object, array, string, number, etc.:

// main.js
promiseWorker.postMessage({
  hello: 'world',
  answer: 42,
  "this is fun": true
}).then(/* ... */);

// worker.js
registerPromiseWorker(function (message) {
  console.log(message); // { hello: 'world', answer: 42, 'this is fun': true }
});

Note that the message will be JSON.stringifyd, so you can't send functions, Dates, custom classes, etc.

Inside of the worker, the registered handler can return either a Promise or a normal value:

// worker.js
registerPromiseWorker(function () {
  return Promise.resolve().then(function () {
    return 'much async, very promise';
  });
});

// main.js
promiseWorker.postMessage(null).then(function (message) {
  console.log(message): // 'much async, very promise'
});

Ultimately, the value that is sent from the worker to the main thread is also stringifyd, so the same format rules apply.

Any thrown errors or asynchronous rejections from the worker will be propagated to the main thread as a rejected Promise. For instance:

// worker.js
registerPromiseWorker(function (message) {
  throw new Error('naughty!');
});

// main.js
promiseWorker.postMessage('whoops').catch(function (err) {
  console.log(err.message); // 'naughty!'
});

Note that stacktraces cannot be sent from the worker to the main thread, so you will have to debug those errors yourself. This library does however, print message to console.error(), so you should see them there.

If you need to send messages of multiple types to the worker, just add some type information to the message you send:

// main.js
promiseWorker.postMessage({
  type: 'en'
}).then(/* ... */);

promiseWorker.postMessage({
  type: 'fr'
}).then(/* ... */);

// worker.js
registerPromiseWorker(function (message) {
  if (message.type === 'en') {
    return 'Hello!';
  } else if (message.type === 'fr') {
    return 'Bonjour!';
  }
});

See .zuul.yml for the full list of tested browsers, but basically:

• Chrome
• Firefox
• Safari 7+
• IE 10+
• Edge
• iOS 8+
• Android 4.4+

If a browser doesn't support Web Workers but you still want to use this library, then you can use PseudoWorker.

This library is not designed to run in Node.

Create a new PromiseWorker, using the given worker.

• worker - the Worker or PseudoWorker to use.

Send a message to the worker and return a Promise.

• message - object - required
  • The message to send.
• returns a Promise

Register a message handler inside of the worker. Your handler consumes a message and returns a Promise or value.

• function
  • Takes a message, returns a Promise or a value.

First:

npm install

Then to test in Node (using an XHR/PseudoWorker shim):

npm test

Or to test manually in your browser of choice:

npm run test-local

Or to test in a browser using SauceLabs:

npm run test-browser

Or to test in PhantomJS:

npm run test-phantom

Or to test with coverage reports:

npm run coverage