noob-event-loop.js

var queue = [];

function enqueue (work) {
  queue.push(work);
}

function dequeue () {
  for (var i = 0; i < queue.length; ++i) void function (work, i) {
    work(
      function (isDone) {
      if (isDone) {
        queue[i] = null;
      }
    }
    );
  }(queue[i], i);
  queue = queue.filter(function (work ) { return null != work; });
  return queue.length;
}

function mySetTimeout (fn, ms) {
  var stop = Date.now() + ms;
  enqueue(function (callback) {
    console.log('poll')
    if (Date.now() >= stop) {
      fn();
      callback(true);
    } else { callback(false); }
  });
}

mySetTimeout(function () {
  var foo = 'bar';
  var o = new Object();
  console.log('500ms');
  mySetTimeout(function () {
    console.log('1000ms');
  }, 1000);
}, 500);

console.log('woo')

// while there are messages continue else break
while (dequeue()) ;