AngularJs

AngularJS - A Javascript framework, perfect for one page applications. It was developed and built by the smart people at Google to serve as a user interafce system as well as a backend tool (well it can chat with the backend). Angularjs makes your site very expressive easily, it has all this built in functionality that you would need a lot of work to achieve otherwise. FYI; there are other frameworks that can achieve some of the functionality in Angularjs, or even more with some.