ReactJS is one of the most popular JavaScript front-end libraries for building user interfaces with a strong foundation. It has a robust and rapidly growing developer community and a declarative, efficient, and flexible library for building reusable UI components. It is an open-source, component-based front-end library responsible only for the application view layer.
Initially, it was developed by Jordan Walke, a software engineer at Facebook and maintained by Facebook. Later, it was used in other Facebook products like WhatsApp & Instagram. Facebook implemented ReactJS in its newsfeed section in 2011, but it was released to the public in May 2013.
The main objective of ReactJS is to develop interactive User Interfaces (UI) with the help of virtual DOM (JavaScript object) to improve application performance because the JavaScript virtual DOM is faster than the regular DOM because, it only changes individual DOM elements instead of reloading complete DOM every time. It uses component and data patterns that improve readability and helps to maintain larger apps.
The components are the heart of all React applications. These component are used to make a React application. Each component is responsible for outputting a small, reusable piece of HTML code and can be nested with other components to allow complicated applications.