REACT BASICS

 

React Basics

React is a powerful JavaScript library for building user interfaces, particularly for single-page applications where data changes over time. It allows developers to create large web applications that can update and render efficiently in response to data changes.

React.js Definition

React.js (or React) is an open-source JavaScript library developed by Facebook for building fast, scalable, and simple user interfaces. It is component-based, which means the UI is built from encapsulated components that manage their own state.

Prerequisites

Before diving into React, you should have a basic understanding of the following:

• HTML/CSS: Understanding the structure and styling of web pages.
• JavaScript: Familiarity with ES6+ syntax, including classes, arrow functions, and destructuring.
• Node.js and npm: Knowing how to use Node.js and npm (Node Package Manager) to manage libraries and dependencies.

Features of React

1. Virtual DOM: React uses a virtual DOM to improve performance. When the state of an object changes, React updates only the virtual DOM, and then it compares it with the previous version and updates the actual DOM only where changes occurred.

2. JSX: JSX stands for JavaScript XML. It allows developers to write HTML within JavaScript, making the code easier to understand and debug.

3. Components: Everything in React is a component. Components are reusable, encapsulated code that defines part of the user interface.

4. Unidirectional Data Flow: React uses a unidirectional data flow, making it easier to debug and understand the data flow in the application.

5. State and Props: Components in React can maintain their own state and receive input via props, allowing for dynamic rendering.

---

React Components

Components are the building blocks of a React application. They represent pieces of the UI that can be reused and combined to create complex user interfaces.

Types of Components

1. Functional Components

   Functional components are simple JavaScript functions that accept props as an argument and return React elements. They are also known as stateless components because they do not manage their own state.

   Example:

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

   Output: "Hello, John!"

2. Class Components

   Class components are ES6 classes that extend from React.Component and can manage their own state and lifecycle methods.

   Example:

   class Welcome extends React.Component {
     render() {
       return <h1>Hello, {this.props.name}!</h1>;
     }
   }
   
   // Usage
   <Welcome name="Jane" />
   

   Output: "Hello, Jane!"