Salesforce has recently launched a new User Interface that is Salesforce Lightning Design System. It gives us very sharp and clean UI. By add JavaScript we can make our Lightning UI even sharper. Here you can find JavaScript

Frameworks which use to make the best design.

1. Appiphony Lightning JS  :

Appiphony Lighting JS(ALJS) gives harness with jQuery Library and Ember to deliver a rich UI experience to our Salesforce Lighting Design System.ALJS is implemented and maintained by Appiphony.
Click here to Getting Started with ALJS.

2) Lightning Dart:

The library for implementing web applications based on the CSS framework Salesforce Lightning Design System is Lighting Dart. Here we can find CSS, icons, and fonts which are useful while implementing Web Applications.
Lightning Dart gives the most complete component functionality for SLDS. Dart compiles into Javascript (“Dart – the better Javascript”), For business functionality, we can write the code in Dart or in Javascript directly – or any language which can call Javascript.

Click here to Getting Started with Lightning Dart.