gistfile1.js

WorkQueue = {
  MAX_CONCURRENT: 2,
  init: function() {
    this.num_working = 0;
    this.items = [];
  },
  push: function(item) {
    this.items.push(item);
    this.update()
  },
  update: function() {
    if (this.items.length > 0 && this.num_working < WorkQueue.MAX_CONCURRENT) {
      var item = this.items.shift();
      this.num_working++;
      item.startWorking(this.itemFinishedHandler.bind(this));
    }
  },
  itemFinishedHandler: function() {
    this.num_working--;
    this.update();
  }.bind(this)
}