Introduction to React.js: Why It Dominates the Modern Web

What is React.js?

React.js is an open-source JavaScript library used for building user interfaces, especially single-page applications where you need a fast, interactive user experience. It allows developers to build reusable UI components that manage their own state and efficiently update when data changes.

Unlike traditional DOM manipulation with vanilla JavaScript or jQuery, React uses a virtual DOM to optimize rendering performance. When state changes occur, React intelligently updates only the components that need to change—resulting in better speed and responsiveness.

Core Concepts of React

Here are a few foundational concepts that make React powerful:

1. Components

Everything in React is a component. Components are independent, reusable pieces of code that return React elements (usually written in JSX). They can be either functional or class-based.

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

2. JSX (JavaScript XML)

JSX is a syntax extension that lets you write HTML-like code in your JavaScript files. It’s syntactic sugar that makes your code more readable and expressive.

const element = <h1>Welcome to React!</h1>;

3. State and Props

Props are used to pass data from parent to child components. State is a built-in object used to store data that can change over time and trigger re-renders.

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

4. Hooks

Introduced in React 16.8, Hooks let you use state and other React features in functional components. Popular hooks include useState, useEffect, and useContext.

useEffect(() => {
  document.title = `Count: ${count}`;
}, [count]);