Using AsyncQueue and Promises to control the order in which expensive assets are loaded in a page

gistfile1.js

// AsyncQueue version
YUI().use('async-queue', function (Y) {

  var queue = new Y.AsyncQueue(
    function () {
      queue.pause();
      // Load a widget
      YUI().use('tabview', function (Y) {
        var tabview = new Y.TabView();
        //...

        // continue to the next step
        queue.run();
      });
    },
    // ...
    function () {
      queue.pause();
      Y.Get.js('http://twitter.com/some/widget.js', function () {
        queue.run();
      });
    }
  );
  queue.run();
});

// Promises version
YUI().use('promise', function (Y) {
  var step = new Y.Promise(function (success) {
    YUI().use('tabview', function (Y) {
      var tabview = new Y.TabView();
      // ...
      success();
    });
  });

  step.then(function () {
    return new Y.Promise(function (success) {
      YUI().use('datatable', 'datasource', function (Y) {
        // ...
        success();
      });
    });
  }).then(function () {
    return new Y.Promise(function (success) {
      Y.Get.js('http://twitter.com/some/widget.js', function () {
        success();
      });
    });
  });
});