Introduction to React

React is a JavaScript library for building modern, interactive user interfaces. It is widely used for developing single-page applications (SPAs) and is maintained by Meta (formerly Facebook).

What is React?

React (also known as React.js or ReactJS) is a front-end JavaScript library designed to create reusable UI components. It focuses on the "view" layer of an application, which means it helps in building what users see and interact with on the screen.

React makes building complex interfaces more manageable by allowing developers to break the UI into small, self-contained pieces called components.

React was created by Jordan Walke, a software engineer at Facebook.

How React Works

React uses a concept called the Virtual DOM (Document Object Model):

  • Instead of updating the real DOM directly, React creates a virtual copy of the DOM in memory.
  • When changes occur, React compares the new virtual DOM with the previous version.
  • It then calculates the most efficient way to update the real DOM and applies only those changes.

This process makes web applications built with React fast and efficient.

What You Should Already Know

Before diving into React, you should be familiar with the following:

  • HTML (HyperText Markup Language)
  • CSS (Cascading Style Sheets)
  • JavaScript (Basic syntax and concepts)

If you’re not confident with these topics, it’s recommended to review them first.

A Brief History of React

  • React was first used internally by Facebook in 2011 for the Newsfeed feature.
  • It was released to the public in July 2013 as version 0.3.0.
  • The latest stable version of React is 19.0.0, released in December 2024.

Since its release, React has grown to become one of the most popular JavaScript libraries for front-end development.

Why Learn React?

  • Component-based architecture that encourages code reusability
  • High performance through the use of the virtual DOM
  • Strong community support and a large ecosystem of tools
  • Used by many major companies, including Facebook, Instagram, Netflix, and Airbnb