If you ignore the Angular part of this article, it applies to JavaScript in general. If you're still using callbacks with $.ajax(, please look into Promises. jQuery has an implementation (though I've heard it doesn't exactly follow the standard.
It will be native in ES6 (the next version of JavaScript)
http://www.2ality.com/2014/10/es6-promises-api.html – this is an in-depth on ES6 promises.
http://kangax.github.io/compat-table/es6/ - even the next IE will have it.
Wrangle Async Tasks With JQuery Promises
The Art of Promise-Based Architecture
Netflix JavaScript Talks - Version 7: The Evolution of JavaScript – go to minute 12:30 to watch about sync, async, callbacks and using promises. ES6 generator feature => yield and function* are also introduced.
Another good Promise article.
“Many of us are using promises without really understanding them.” We have a problem with promises.
Promises reminds me of async/await in C#, are easier (in my opinion) to manage and maintain than callbacks, and are the new/current/future way to do asynchronous tasks in JavaScript.
It’s well worth the time to learn how to use them.