What is React.Js?

React.js, or React, is a JavaScript library for building user interfaces (UIs) for web applications. It's free, open-source, and maintained by Meta (formerly Facebook) and a community of developers. 

React is used to create interactive UIs by designing simple views for each state in an application. It's known for being efficient, flexible, and declarative. Some of its key features include: 

·         Component-based: React components manage their own state and can be composed to create complex UIs. 

·         One-way data binding: Data flows from parent components to child components. 

·         Rendering: React only re-renders the parts of the page that have changed. 

·         Reusable components: React's ability to create reusable components makes it ideal for rapid prototyping. 

React can be used to develop single-page, mobile, or server-rendered applications. Some examples of how React is used include: 

·         Instagram and Facebook: React is responsible for the responsiveness and speed of these apps. 

·         Airbnb: React components work together to create a seamless user experience from browsing to booking. 

·         Stock trading platforms and live chat boxes: React is commonly used in situations where performance is key.