Mastering JavaScript Promises

The solution – introducing promises in jQuery

The solution to the preceding problem was finally delivered in jQuery 1.5 as the deferred object. Before the deferred concept was introduced in jQuery, the typical AJAX call was something like this:

$.ajax({
  url: "/testURL.com",
  Success: TheSuccessFunction,
  Error: TheErrorFunction
});

Can you guess what could be the output of this function? Yes, a single XMLHttpRequest object, which is quite expected for those who are still maintaining the apps built before jQuery 1.5.

Now, what dramatical change was introduced in jQuery 1.5. First of all, it's based on a specification of common JavaScript that defines common interfaces and can be extended as per the needs, and secondly, they are quite global and you ...