Lazy Load

Lazy Load is a technique in web development that defers the loading of non-critical resources until they are needed. Instead of loading all the content when the page is first accessed, lazy loading delays the loading of elements like images, videos, or other heavy components until the user actually needs them, such as when they scroll to that part of the page. This technique is widely used to improve page performance and enhance the user experience.

Benefits of Lazy Load

  1. Improved Page Load Speed:

    • By loading only essential resources initially, the page's initial load time is significantly reduced, allowing users to access the content more quickly.

  2. Bandwidth Savings:

    • Loading only the resources that are needed at any given time reduces the amount of data transferred, which is particularly beneficial for mobile users.

  3. Reduced Server Load:

    • The server does not need to handle a large number of requests simultaneously, thus reducing server load and improving overall performance.

  4. Enhanced User Experience:

    • Faster initial load times and smooth interactions lead to higher user satisfaction.

Examples of Lazy Load Implementation

  1. Images:

    • Load images only when they enter the viewport, delaying the loading of off-screen images.

    <img src="placeholder.jpg" data-src="actual-image.jpg" alt="Lazy Loaded Image" class="lazy"> <script> document.addEventListener("DOMContentLoaded", function() { let lazyImages = [].slice.call(document.querySelectorAll("img.lazy")); if ("IntersectionObserver" in window) { let lazyImageObserver = new IntersectionObserver(function(entries, observer) { entries.forEach(function(entry) { if (entry.isIntersecting) { let lazyImage = entry.target; lazyImage.src = lazyImage.dataset.src; lazyImage.classList.remove("lazy"); lazyImageObserver.unobserve(lazyImage); } }); }); lazyImages.forEach(function(lazyImage) { lazyImageObserver.observe(lazyImage); }); } }); </script>

  2. Videos:

    • Load the video only when the play button is pressed, reducing the data usage during the initial page load.

    <video controls width="600" class="lazy"> <source data-src="video.mp4" type="video/mp4"> Your browser does not support HTML5 video. </video> <script> document.addEventListener("DOMContentLoaded", function() { let videoElements = document.querySelectorAll("video.lazy"); videoElements.forEach(function(video) { video.addEventListener("play", function() { let source = video.querySelector("source"); source.src = source.dataset.src; video.load(); }, { once: true }); }); }); </script>

  3. Infinite Scroll:

    • Dynamically load new content as the user scrolls down the page, allowing for efficient display of large amounts of content.

    document.addEventListener('scroll', function() { if (window.innerHeight + window.scrollY >= document.body.offsetHeight) { // Load more content here } });

Summary

Lazy load is a crucial technique for optimizing web page and web application performance, particularly effective for resources like images, videos, and long lists or tables. By implementing lazy load correctly, page load speeds improve, bandwidth is conserved, and server load is reduced, all contributing to a better user experience.