Mastering React.js: The Essential Guide

All About React.js

1. What is React.js?
React.js is a popular JavaScript library for building user interfaces, particularly for
single-page applications. It enables developers to create reusable UI components
and efficiently manage the state of complex applications.

 Created by Facebook.
 Component-based and declarative.
 Utilizes a virtual DOM for performance optimization.



2. Features of React.js
1. Component-Based Architecture:
o Applications are built using encapsulated components that manage
their own state.
2. Declarative Syntax:
o Describes what the UI should look like based on the application state.


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

3. Virtual DOM:
o Updates only the parts of the DOM that have changed, enhancing
performance.
4. One-Way Data Binding:
o Data flows in a single direction, making the application easier to
debug.
5. JSX:
o Combines HTML and JavaScript into a single syntax.


const element = <button>Click Me!</button>;

, 3. Setting Up a React Project
1. Using Create React App:
o The easiest way to start a React project.


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

2. Manual Setup:
o Install React and ReactDOM.


npm install react react-dom

3. Using a CDN (for simple demos):

<script
src="https://unpkg.com/react@17/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@17/umd/react-
dom.development.js"></script>


4. Core Concepts of React.js
1. Components:
o Reusable and independent pieces of UI.
o Functional Component:


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

o Class Component:

class Welcome extends React.Component {
render() {
return <h1>Hello, World!</h1>;
}
}