What is React?

React is an open-source JavaScript library used to build user interfaces (UI), especially single-page applications (SPAs).

It was developed and is maintained by Meta (Facebook).

In simple words: React helps developers create fast, reusable, and interactive UI components.

Why Was React Created?

Before React, updating UI elements dynamically was slow and complex. Traditional JavaScript manipulated the DOM directly, which caused performance issues in large applications.

React was created to:

• Improve performance
• Simplify UI development
• Make code reusable and maintainable

Key Features of React

1. Component-Based Architecture

React applications are built using components. Each component represents a small, reusable piece of UI.

Example:

• Header component
• Footer component
• Button component

This makes development faster and easier to manage.

2. Virtual DOM

React uses a Virtual DOM, which is a lightweight copy of the real DOM.

• React updates only the required parts of the UI
• Improves performance
• Reduces unnecessary DOM operations

3. Declarative UI

In React, you simply describe what the UI should look like, and React takes care of updating it when data changes.

This makes code:

• Easier to read
• Easier to debug
• More predictable

4. JSX (JavaScript XML)

React uses JSX, which allows you to write HTML-like code inside JavaScript.

Example:

const element = <h1>Hello, React!</h1>;

JSX makes UI code more readable and developer-friendly.

5. One-Way Data Binding

React follows one-way data flow, meaning data moves from parent to child components.

This ensures:

• Better control over data
• Fewer bugs
• Easier debugging

Is React a Framework or a Library?

React is a library, not a framework.

• It focuses only on the UI layer
• You can choose additional tools for routing, state management, and API handling

Example tools:

• React Router
• Redux / Context API
• Axios / Fetch API

Where is React Used?

React is widely used in:

• Single Page Applications (SPAs)
• Dashboards
• Admin Panels
• E-commerce platforms
• Social media applications
• SaaS products

Popular websites using React:

• Facebook
• Instagram
• Netflix
• WhatsApp Web
• Airbnb

Advantages of React

• Fast performance
• Reusable components
• Strong community support
• Easy to learn for JavaScript developers
• SEO-friendly with SSR (Next.js)

Who Should Learn React?

React is ideal for:

• Frontend developers
• Full-stack developers
• UI/UX-focused developers
• Freshers entering web development
• Developers working on modern web apps

React in Interviews (Quick Answer)

What is React?

React is an open-source JavaScript library developed by Meta for building fast, scalable, and interactive user interfaces using a component-based architecture.