React Introduction

What is React?

React is a front-end JavaScript library.

It was developed by the Facebook Software Engineer Jordan Walke.

React is also known as React.js or ReactJS.

React is a tool for building UI components.

How does React Work?

React creates a VIRTUAL DOM in memory.

Instead of manipulating the browser's DOM directly, React creates a virtual DOM where it does all the necessary calculations before updating the browser DOM.

React only changes what needs to be changed!

It finds out what changes have been made, and updates only those parts.

What You Should Already Know

Before you continue, you should have a basic understanding of:

• HTML
• CSS
• JavaScript

React.JS History

Latest version of React.JS is 19.0.0 (December 2024).

Initial public release (version 0.3.0) was in July 2013.

React.JS was first used in 2011 for Facebook's Newsfeed feature.

Facebook Software Engineer, Jordan Walke, created it.

React Hello World Example

Here is a simple React component example:

import { createRoot } from 'react-dom/client';

function Hello() {
  return (
    
Hello World!
  );
}

createRoot(document.getElementById('root')).render(
  
);