Components in React: Functional vs. Class Components

What are React Components?

React components are reusable building blocks for UI. They allow you to break down a UI into smaller, independent pieces.

Types of Components in React

React has two types of components:

1. Functional Components (Modern, recommended)
2. Class Components (Older)

1. Functional Components (Recommended)

Functional components are JavaScript functions that return JSX.

Example of a Functional Component:

function Greeting() {
  return <h1>Hello, React!</h1>;
}

export default Greeting;

Why Use Functional Components?

• Simpler and easier to read
• No need for this keyword
• Hooks (useState, useEffect) work only in functional components

2. Class Components (Older Method)

Class components use ES6 classes and render() to return JSX.

Example of a Class Component:

import React, { Component } from "react";

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

export default Greeting;

Why Avoid Class Components?

• More complex syntax
• this keyword can be confusing
• Cannot use hooks like useState directly

State in Components

✅ State in Functional Components (Using useState)

import { useState } from "react";

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

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increase</button>
    </div>
  );
}

export default Counter;

❌ State in Class Components (Using this.state)

import React, { Component } from "react";

class Counter extends Component {
  constructor() {
    super();
    this.state = { count: 0 };
  }

  increaseCount = () => {
    this.setState({ count: this.state.count + 1 });
  };

  render() {
    return (
      <div>
        <p>Count: {this.state.count}</p>
        <button onClick={this.increaseCount}>Increase</button>
      </div>
    );
  }
}

export default Counter;

Functional components with hooks (useState) are shorter and cleaner!

Props in Components

✅ Using Props in Functional Components

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

// Usage
<Welcome name="Alice" />;

❌ Using Props in Class Components

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

// Usage
<Welcome name="Alice" />;

Functional vs. Class Components: Comparison

Conclusion

• Use functional components for better performance and readability.
• Functional components support React Hooks (useState, useEffect).
• Class components are outdated and should be avoided unless working with legacy code.