AsynchEventDispatcher.js

function AsynchDispatcher() {
  var listeners = [],
      m = 'message',
      w = window;

  function receiveMessage(index) {
    index = parseInt(index.data || index);

    setTimeout(listeners[index], 10);
    if (index) {
      w.postMessage(index - 1, location.origin);
    } else {
      w.removeEventListener(m, receiveMessage, false);
    }
  }

  function add(listener) {
    listeners.push(listener);
  }

  function fire() {
    w.addEventListener(m, receiveMessage, false)
    receiveMessage(listeners.length - 1);
  }

  this.add = add;
  this.fire = fire;
}

var d = new AsynchDispatcher();
var total = 25000;
var i = total;

var count = 0;
while (i--) {
  d.add((function(i) {
    return function() {
      if (0 == count) {
        console.log("Started at %o", new Date());
      }
      count++;
      if (count == total - 1) {
        console.log("Finished at %o", new Date());
      }
    }
  })(i));
}
d.fire();