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Introduction to React.js

📘 React.js 👁 115 views 📅 Nov 05, 2025
⏱ Estimated reading time: 2 min

React.js is a JavaScript library used to build user interfaces, especially for single-page applications. It was developed by Facebook (Meta) and focuses on creating fast, interactive, and reusable UI components.

Key Features

  • Component-Based: Build encapsulated, reusable UI components.

  • Declarative: Describe what the UI should look like; React handles updates.

  • Fast Performance: Uses a Virtual DOM to efficiently update the UI.

  • Reusable Logic: Components and hooks allow clean code reuse.

  • Large Ecosystem: Strong community and wide library support.

Core Concepts

Components

Components are independent pieces of UI.

function Welcome() {
  return <h1>Hello, React</h1>;
}

JSX

JSX allows writing HTML-like syntax inside JavaScript.

const element = <h1>Hello World</h1>;

Props

Props pass data to components.

function Greeting({ name }) {
  return <h1>Hello, {name}</h1>;
}

State

State manages data that changes over time.

import { useState } from "react";

function Counter() {
  const [count, setCount] = useState(0);
  return <button onClick={() => setCount(count + 1)}>{count}</button>;
}

Hooks

Hooks add React features to functional components.
Common hooks include useState, useEffect, and useContext.

How React Works

  1. User interacts with the UI

  2. State changes

  3. Virtual DOM updates

  4. Real DOM updates efficiently

Getting Started

npm create vite@latest my-app
cd my-app
npm install
npm run dev

Use Cases

  • Web applications with dynamic content

  • Dashboards and admin panels

  • Large-scale front-end projects

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