setTimeout via Web Worker

overrides.js

var timeoutId = 0;
var timeouts = {};

var worker = new Worker("/static/timeout-worker.js");
worker.addEventListener("message", function(evt) {
  var data = evt.data,
      id = data.id,
      fn = timeouts[id].fn,
      args = timeouts[id].args;

  fn.apply(null, args);
  delete timeouts[id];
});

window.setTimeout = function(fn, delay) {
  var args = Array.prototype.slice.call(arguments, 2);
  timeoutId += 1;
  delay = delay || 0;
  var id = timeoutId;
  timeouts[id] = {fn: fn, args: args};
  worker.postMessage({command: "setTimeout", id: id, timeout: delay});
  return id;
};

window.clearTimeout = function(id) {
  worker.postMessage({command: "clearTimeout", id: id});
  delete timeouts[id];
};

timeout-worker.js

var timers = {};

function fireTimeout(id) {
  this.postMessage({id: id});
  delete timers[id];
}

this.addEventListener("message", function(evt) {
  var data = evt.data;

  switch (data.command) {
  case "setTimeout":
    var time = parseInt(data.timeout || 0, 10),
        timer = setTimeout(fireTimeout.bind(null, data.id), time);
    timers[data.id] = timer;
    break;
  case "clearTimeout":
    var timer = timers[data.id];
    if (timer) clearTimeout(timer);
    delete timers[data.id];
  }
});