Introduction to React.js: A Beginner’s Guide

React.js, developed and maintained by Facebook, is a powerful and widely-used JavaScript library for building user interfaces—especially single-page applications where you need a dynamic, responsive user experience.

📌 What is React.js?

React is a component-based JavaScript library used to create interactive UIs. Unlike traditional approaches that update the whole DOM, React uses a Virtual DOM to update only the parts that have changed—resulting in faster performance.

🔥 Why React is So Popular

Reusable Components
Code once, use anywhere. Components make development efficient and scalable.
Virtual DOM
Makes UI updates fast and smooth.
Strong Community
Backed by Facebook and a large developer base, it has massive support and thousands of packages.
SEO-Friendly
With tools like Next.js (built on top of React), apps can be rendered server-side for better SEO.

🛠️ Setting Up a React Project

You can get started quickly using Create React App:

bashCopyEditnpx create-react-app my-app
cd my-app
npm start

This sets up a development server and opens your app in the browser.

🧱 React Basics: Components

A simple component looks like this:

jsxCopyEditfunction Welcome(props) {
  return <h1>Hello, {props.name}</h1>;
}

And it’s used like this:

jsxCopyEdit<Welcome name="John" />

🔄 State and Props

Props are used to pass data from parent to child.
State is used to manage internal component data.

Example with state:

jsxCopyEditimport { useState } from 'react';

function Counter() {
  const [count, setCount] = useState(0);

  return (
    <>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>Click me</button>
    </>
  );
}

🌐 React Ecosystem

React by itself handles the UI, but the ecosystem is vast:

React Router – for navigation
Redux / Zustand / Recoil – for state management
Next.js – for server-side rendering
React Query / SWR – for data fetching

💡 Final Thoughts

React continues to dominate front-end development because of its simplicity, flexibility, and performance. Whether you’re building a personal portfolio or a massive web app, React is an excellent choice.