Facebook and Instagram brings Javascript Library “React” for creating user interfaces (UI). React is developed for Web, iOS and Android applications. Many people choose React to building large scale applications.

react-javascript-library-for-building-user-interface
react-javascript-library-for-building-user-interface

React uses two major ideas
i-  Simple
ii- Declarative

React uses a lot of features
i- Vitual DOM for very high performance
ii- Minimal changes to up-to-date your DOM
iii- Implements one-way data flow to binding data easily
iv- Very efficient and flexible work with libraries and frameworks
v- Uses JSX Syntax (makes more code readable/writing)

Downloads:

Github Links:
https://github.com/facebook/react
http://facebook.github.io/react/
https://facebook.github.io/react/downloads.html

Documentation:
https://facebook.github.io/react/docs/getting-started.html