React JS - Library for Building User Interfaces

React is a  free and open-source front-end JavaScript library, which is used to develop both web and mobile apps. It is used for handling the view layer for web and mobile apps. It gives you the ability to create reusable UI components. 

It is used to create large web applications that can change data, without reloading the page. It is a simple, fast and scalable library. 

The main features of React include:

• JSX 
• Virtual Document Object Model (DOM)
• Architecture 
• Extensions
• Data Binding 
• Debugging
• Fast and Simple
• Component Based