Lazy Loading Images

Introduction

Lazy loading is a design pattern that postpones the loading of resources until they are needed, improving performance and user experience. This lesson focuses on lazy loading images, which is crucial for optimizing web performance.

What is Lazy Loading?

Lazy loading is a technique that prevents images from loading until they enter the viewport (the visible area of the web page). This reduces initial load time, saves bandwidth, and enhances user experience.

Why Use Lazy Loading?

• Improves Page Load Speed
• Reduces Bandwidth Usage
• Enhances User Experience
• Decreases Server Load

How to Implement Lazy Loading

Using Native Lazy Loading

Modern browsers support native lazy loading through the `loading` attribute. To implement, simply add `loading="lazy"` to your `` tags.

<img src="image.jpg" alt="Description" loading="lazy">

Using JavaScript for Lazy Loading

If you need more control or want to support older browsers, you can implement lazy loading using JavaScript.

const images = document.querySelectorAll('img[data-src]');
const imgObserver = new IntersectionObserver((entries, observer) => {
    entries.forEach(entry => {
        if (entry.isIntersecting) {
            const img = entry.target;
            img.src = img.dataset.src;
            imgObserver.unobserve(img);
        }
    });
});
images.forEach(img => {
    imgObserver.observe(img);
});
            

Best Practices

• Use the `loading` attribute for native support.
• Optimize images for web before lazy loading.
• Provide a placeholder or low-quality image to enhance perceived loading time.
• Test on multiple devices to ensure proper functionality.

FAQ