ReactJS

React was created by jorden walk, and it is maintained by Facebook and the community of individual developer.

ReactJS is a declarative, efficient, and flexible JavaScript library for building reusable UI components.

It is an open-source, component-based front end library responsible only for the view layer of the application.

It is used for designing user-interface specifically for Single Page Applications.

React is a JavaScript framework. Using the framework is as simple as including a JavaScript file in our HTML and using the React exports in our application's JavaScript.

Most of the websites are built using MVC (model view controller) architecture. In MVC architecture, React is the 'V' which stands for view, whereas the architecture is provided by the Redux or Flux.

A ReactJS application is made up of multiple components, each component responsible for outputting a small, reusable piece of HTML code. The components are the heart of all React applications. These Components can be nested with other components to allow complex applications to be built of simple building blocks. ReactJS uses virtual DOM based mechanism to fill data in HTML DOM. The virtual DOM works fast as it only changes individual DOM elements instead of reloading complete DOM every time.