React JS is a JavaScript library developed by Facebook, which was used to build Instagram and among other things. React is used by developers to create better user interface for websites and applications.
Companies that use React JS is Netflix, UberEATS, PayPal and so much more! While it is possible to create programs and applications with JavaScript alone, projects created with React JS are easier to scale. When I mean by scale, the code is easier to write out and easier to understand and maintain.
One part that is important to React JS is components. Components are independent bits of code that are reusable in the program. While they compute as JavaScript functions, they work in isolation and return in HTML format.
Components come in two types: class and function components. Both class and function components work similarly, but function components are written in less code and are easier to understand. Function components are preferred more due to its capability.