Bootstrap

Introduction

Bootstrap is a popular front-end framework for building responsive, mobile-first websites quickly.

It provides:

Pre-designed CSS classes for layout, typography, forms, buttons, and more
JavaScript components like modals, carousels, and dropdowns
A grid system to create responsive designs easily

Why use Bootstrap?

Saves time with ready-to-use components
Consistent design across browsers
Works well for beginners and professionals

Step 1: Include Bootstrap in Your Project

You can include Bootstrap via CDN (quick) or download the files.

Using CDN (Bootstrap 5):

Add this in the <head> of your HTML:

<!-- Bootstrap CSS -->
<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/css/bootstrap.min.css" rel="stylesheet">

<!-- Bootstrap JS Bundle (includes Popper) -->
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js"></script>

✅ No installation required. Just include these links and you’re ready to go.

Step 2: Basic HTML Structure with Bootstrap

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Bootstrap Example</title>
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/css/bootstrap.min.css" rel="stylesheet">
</head>
<body>

    <div class="container">
        <h1 class="text-center mt-5">Welcome to Bootstrap</h1>
        <p class="text-muted text-center">Build responsive websites quickly!</p>
    </div>

    <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js"></script>
</body>
</html>

.container → Centers content and adds padding
.text-center → Centers text
.mt-5 → Adds top margin (mt = margin top, 5 = spacing scale)

Step 3: Bootstrap Grid System

Bootstrap uses a 12-column grid system to create responsive layouts.

Example: 3-Column Layout

<div class="container">
    <div class="row">
        <div class="col-md-4 bg-primary text-white text-center p-3">Column 1</div>
        <div class="col-md-4 bg-success text-white text-center p-3">Column 2</div>
        <div class="col-md-4 bg-danger text-white text-center p-3">Column 3</div>
    </div>
</div>

.row → Wraps columns
.col-md-4 → Column width (4/12) on medium and larger screens
Columns stack automatically on smaller screens

Step 4: Bootstrap Components

Buttons

<button class="btn btn-primary">Primary</button>
<button class="btn btn-success">Success</button>
<button class="btn btn-danger">Danger</button>

Alerts

<div class="alert alert-warning" role="alert">
    This is a warning alert!
</div>

Navbar

<nav class="navbar navbar-expand-lg navbar-dark bg-dark">
  <div class="container-fluid">
    <a class="navbar-brand" href="#">MySite</a>
    <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav">
      <span class="navbar-toggler-icon"></span>
    </button>
    <div class="collapse navbar-collapse" id="navbarNav">
      <ul class="navbar-nav ms-auto">
        <li class="nav-item"><a class="nav-link active" href="#">Home</a></li>
        <li class="nav-item"><a class="nav-link" href="#">About</a></li>
        <li class="nav-item"><a class="nav-link" href="#">Contact</a></li>
      </ul>
    </div>
  </div>
</nav>

Step 5: Responsive Utilities

Bootstrap provides classes to show/hide elements or adjust layouts for different screen sizes:

A simple Bootstrap page with navbar, grid, and buttons:

Example Code:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Bootstrap Practice</title>
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/css/bootstrap.min.css" rel="stylesheet">
</head>
<body>

    <!-- Navbar -->
    <nav class="navbar navbar-expand-lg navbar-dark bg-dark">
      <div class="container-fluid">
        <a class="navbar-brand" href="#">MySite</a>
        <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav">
          <span class="navbar-toggler-icon"></span>
        </button>
        <div class="collapse navbar-collapse" id="navbarNav">
          <ul class="navbar-nav ms-auto">
            <li class="nav-item"><a class="nav-link active" href="#">Home</a></li>
            <li class="nav-item"><a class="nav-link" href="#">About</a></li>
            <li class="nav-item"><a class="nav-link" href="#">Contact</a></li>
          </ul>
        </div>
      </div>
    </nav>

    <!-- Header -->
    <div class="container text-center mt-5">
        <h1>Welcome to Bootstrap</h1>
        <p class="text-muted">Responsive and fast front-end framework</p>
    </div>

    <!-- Grid Layout -->
    <div class="container mt-4">
        <div class="row">
            <div class="col-md-4 bg-primary text-white text-center p-3">Column 1</div>
            <div class="col-md-4 bg-success text-white text-center p-3">Column 2</div>
            <div class="col-md-4 bg-danger text-white text-center p-3">Column 3</div>
        </div>
    </div>

    <!-- Buttons -->
    <div class="container text-center mt-4">
        <button class="btn btn-primary m-2">Primary</button>
        <button class="btn btn-success m-2">Success</button>
        <button class="btn btn-danger m-2">Danger</button>
    </div>

    <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js"></script>
</body>
</html>

Bootstrap

Introduction

Example Code:

Bootstrap

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