React Components

What is Components?

React components are reusable and independent building blocks that define parts of a user interface. They let you split the UI into independent, reusable pieces that can be managed and developed separately.

A component is a JavaScript function or class that:

Returns a piece of JSX (JavaScript XML).
Represents part of the UI.
Can manage its own state and handle events.

Types of React Components

There are two main types of components in React:

a) Functional Components (modern & preferred)

function Notebook(){
    return(
        <>
            <h1>Hello, Welcome to Dev Notebook</h1>
        </>
    )
}

export default Notebook

Or using arrow functions:

const Welcome = () => <h1>Hello, world!</h1>;

b) Class Components (older way)

import React, { Component } from 'react';

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

export default Welcome

Why Use Components?

Reusability: Build once, reuse everywhere.
Maintainability: Small components are easier to manage.
Separation of concerns: UI and logic stay organized.

Component with `props`

Props are used to receive data from parent components.

function AboutMe(props){
    return(
        <>
            <h1>Hello, my name is {props.username}</h1>
        </>
    )
}

export default AboutMe


// call the component
<AboutMe username="Nitin" />

Component with `State`

State is data that changes over time and affects what a component displays.

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

React Components

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