React.js: A Beginner’s Guide to Building Modern Web Applications
React.js is a popular JavaScript library for building dynamic and interactive user interfaces. Developed by Meta (Facebook), React enables developers to create scalable and high-performance single-page applications (SPAs).
Discover more at RedSysTech React.js Guide.
What is React.js?
- React.js is an open-source JavaScript library used for building UI components.
- Developed by Facebook (Meta) and released in 2013.
- Uses Virtual DOM for efficient rendering and performance.
- Allows developers to create reusable UI components.
Learn more about What is React.js?.
Why Choose React.js for Web Development?
- Component-Based Architecture – Build reusable UI elements.
- Fast Rendering – Uses a Virtual DOM for optimized performance.
- Strong Community Support – Backed by Meta and open-source contributors.
- SEO-Friendly – Supports server-side rendering (SSR) with Next.js.
Explore Why Developers Choose React.js.
Setting Up React.js
1. Install Node.js & NPM
- Download Node.js from nodejs.org.
- Verify installation:
bash
node -v
npm -v
2. Create a React App Using Create React App (CRA)
bash
npx create-react-app my-app
cd my-app
npm start
Learn How to Set Up React.js.
Understanding React.js Components
1. Functional Component
jsx
function Greeting() {
return <h1>Hello,
React!</h1>;
}
2. Class Component
jsx
class Welcome extends React.Component {
render() {
return <h1>Welcome to React.js!</h1>;
}
}
Explore React.js Component Basics.
JSX – JavaScript XML in React.js
- JSX allows writing HTML-like syntax inside JavaScript.
- Example of JSX in React:
jsx
const element = <h1>Hello, JSX!</h1>;
Learn How JSX Works in React.js.
React.js State & Props
1. React Props (Passing Data to Components)
jsx
function Welcome(props) {
return <h1>Hello, {props.name}!</h1>;
}
2. React State (Managing Component Data)
jsx

React.js Lifecycle Methods
Lifecycle Method | Purpose | Example |
---|---|---|
componentDidMount() | Executes when the component is mounted | Fetching API data |
componentDidUpdate() | Runs when component updates | Updating DOM elements |
componentWillUnmount() | Executes before component removal | Cleanup operations |
Learn React Lifecycle Methods.
React Router – Navigation in React.js
1. Install React Router
bash
npm install react-router-dom
2. Create Routes

React.js vs Other Frontend Frameworks
Feature | React.js | Angular | Vue.js |
---|---|---|---|
Type | Library | Framework | Framework |
Learning Curve | Easy | Steep | Moderate |
Performance | Fast | Moderate | Fast |
Best For | UI Components & SPAs | Enterprise Apps | Small to Medium Projects |
Check out React.js vs Angular vs Vue.
Real-World Applications of React.js
1. Social Media Apps
- Facebook, Instagram use React for dynamic UIs.
2. E-Commerce Websites
- Amazon, Shopify, Flipkart rely on React for fast shopping experiences.
3. Dashboards & Analytics
- Used in admin panels and data visualization apps.
Explore React.js Use Cases.
Career Opportunities for React.js Developers
1. Frontend Developer
- Works on UI development using React.js.
2. Full-Stack Developer
- Uses React for frontend & Node.js for backend.
3. UI/UX Developer
- Builds interactive and accessible web interfaces.
Explore React Developer Careers.