A Full-screen Bootstrap Carousel with Random Initial Image

This article demonstrates building two simple Bootstrap carousel extensions: a full-screen slideshow and a carousel with a randomized initial slide. We'll start with a basic carousel and then enhance it.

Key Concepts:

• Full-Screen Carousel: Achieved using custom jQuery to dynamically adjust carousel item heights to match the window height, and setting background images and colors. A "full-screen" CSS class handles background styling.
• Randomized Initial Slide: Determines the total number of slides, generates a random number, and then applies the "active" class to the corresponding slide and indicator.

Building the Basic Carousel:

Bootstrap provides the core carousel structure. Each image includes a data-color attribute for fallback background color if image loading fails:

<div id="carouselExampleIndicators" class="carousel slide" data-ride="carousel">
  <ol class="carousel-indicators">
    <li data-target="https://www.php.cn/link/de1d5674932fce63c24dc80f6f1ffe9f" data-slide-to="0"></li>
    <li data-target="https://www.php.cn/link/de1d5674932fce63c24dc80f6f1ffe9f" data-slide-to="1"></li>
    <li data-target="https://www.php.cn/link/de1d5674932fce63c24dc80f6f1ffe9f" data-slide-to="2"></li>
  </ol>
  <div class="carousel-inner">
    <div class="carousel-item">
      <img src="/static/imghwm/default1.png"  data-src="https://img.php.cn/upload/article/000/000/000/173958517524890.jpg?x-oss-process=image/resize,p_40"  class="lazy" alt="A Full-screen Bootstrap Carousel with Random Initial Image " />
      <div class="carousel-caption d-none d-md-block">
        <h5 id="First-Image">First Image</h5>
      </div>
    </div>
    <div class="carousel-item">
      <!-- ... more slides ... -->
    </div>
    <div class="carousel-item">
      <!-- ... more slides ... -->
    </div>
  </div>
  <a class="carousel-control-prev" href="https://www.php.cn/link/de1d5674932fce63c24dc80f6f1ffe9f" role="button" data-slide="prev">
    <span class="carousel-control-prev-icon" aria-hidden="true"></span>
    <span class="sr-only">Previous</span>
  </a>
  <a class="carousel-control-next" href="https://www.php.cn/link/de1d5674932fce63c24dc80f6f1ffe9f" role="button" data-slide="next">
    <span class="carousel-control-next-icon" aria-hidden="true"></span>
    <span class="sr-only">Next</span>
  </a>
</div>

JavaScript initializes the carousel, setting the interval and disabling pausing:

$('.carousel').carousel({
  interval: 6000,
  pause: false
});

Creating a Full-Screen Slideshow:

This enhancement uses custom jQuery:

let $item = $('.carousel-item');
let $wHeight = $(window).height();

$item.height($wHeight);
$item.addClass('full-screen');

$('.carousel img').each(function() {
  let $src = $(this).attr('src');
  let $color = $(this).attr('data-color');
  $(this).parent().css({
    'background-image': 'url(' + $src + ')',
    'background-color': $color
  });
  $(this).remove();
});

$(window).on('resize', function() {
  $wHeight = $(window).height();
  $item.height($wHeight);
});

And CSS:

.full-screen {
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
}

This code iterates through images, sets background images and colors on their parent containers, removes the <img alt="A Full-screen Bootstrap Carousel with Random Initial Image" > elements (as backgrounds are now used), and adjusts heights on window resize. The initial slide's active class is added via jQuery for smoother transitions.

Randomizing the Initial Slide:

To display a random slide on load, remove the hardcoded active class from the HTML and add this jQuery:

let $numberOfSlides = $('.carousel-item').length;
let $currentSlide = Math.floor(Math.random() * $numberOfSlides);

$('.carousel-indicators li').each(function() {
  let $slideValue = $(this).attr('data-slide-to');
  if ($currentSlide == $slideValue) {
    $(this).addClass('active');
    $item.eq($slideValue).addClass('active');
  } else {
    $(this).removeClass('active');
    $item.eq($slideValue).removeClass('active');
  }
});

This code selects a random slide and applies the active class to both the corresponding slide and indicator.

Further Customization Ideas:

• Add animation effects (fade, scale) using CSS transitions or JavaScript animation libraries.
• Implement image overlays.
• Randomize the next/previous slides using the slide.bs.carousel event.

This enhanced approach provides more dynamic and engaging carousels. Remember to include the necessary Bootstrap CSS and JavaScript files.

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