workerjs

workerjs

Server Web Workers for node.js that work.

Installation

This module is installed via npm:

$ npm install workerjs

Background

Web Workers are part of the HTML 5 spec and:

defines an API that allows Web application authors to spawn background workers running scripts in parallel to their main page. This allows for thread-like operation with message-passing as the coordination mechanism

In effect, it allows you to get the benefit of multi-talking and multi-threading in single-threaded Javascript, as well as the safety of the event loop.

You can achieve this in node.js using the child_process.fork method, but then you have to use a different API.

This module normalizes the Web Worker API for server-side javascript in node.js with the hopes that we can build more multi-tasking modules built on the Web Worker standard that will work on both the server and the client-side using browserify.

Example Usage

By using Web Workers you can do CPU-intensive operations without blocking the event-loop and incoming IO:

// app.js - run with "node app.js"
var worker = new Worker('/path/to/fibworker.js');
worker.onmessage = function (msg) {
  expect(msg.data).to.equal(1346269);
};
worker.postMessage(30);

// fibworker.js - CPU web worker code
self.onmessage = function (msg) {
  self.postMessage(fibo(msg.data));
};

function fibo (n) {
  return n > 1 ? fibo(n - 1) + fibo(n - 2) : 1;
}

Node Mode - allowing require()

I've also added a "node-friendly" option that allows the Web Worker to use require() and other node.js conventions. To use this, just pass a boolean value of true through to the second argument of the Worker contructor:

// app.js - run with "node app.js"
var worker = new Worker('/path/to/gammaworker.js', true);
worker.addEventListener('message', function (msg) {
  expect(msg.data).to.equal(87178291200.00021);
  done();
});
worker.postMessage(15);

// gammaworker.js - uses require
var gamma = require('gamma');
self.onmessage = function (msg) {
  postMessage(gamma(msg.data));
};

Also, if you provide a module.exports function it will be executed as an entry point of the web worker. This emulates the browserify transform behaviour in webworkify:

// app.js - run with "node app.js"
var worker = new Worker('/path/to/gammaworker2.js', true);
worker.addEventListener('message', function (msg) {
  expect(msg.data).to.equal(87178291200.00021);
  done();
});
worker.postMessage(15);

// gammaworker2.js - uses require
var gamma = require('gamma');

module.exports = function () {
  postMessage(gamma(msg.data));
};