在HTML中,懒加载(Lazy Load)是一种延迟加载图片或其他资源的技术,它可以提高页面的加载速度和性能。下面是一种实现懒加载的方法:
- 设置默认占位图片:在HTML中,为要延迟加载的图片设置一个默认的占位符图片,它将在图片加载之前显示。
<img src="placeholder.jpg" data-src="image.jpg" alt="Lazy Load Image">
- 添加JavaScript代码:为了实现懒加载,我们需要使用JavaScript来检测图片是否在视口(Viewport)中可见,如果是则加载实际图片。
document.addEventListener("DOMContentLoaded", function() {var lazyImages = [].slice.call(document.querySelectorAll("img[data-src]"));if ("IntersectionObserver" in window) {var lazyImageObserver = new IntersectionObserver(function(entries, observer) {entries.forEach(function(entry) {if (entry.isIntersecting) {var lazyImage = entry.target;lazyImage.src = lazyImage.dataset.src;lazyImage.classList.remove("lazy");lazyImageObserver.unobserve(lazyImage);}});});lazyImages.forEach(function(lazyImage) {lazyImageObserver.observe(lazyImage);});} else {// 如果浏览器不支持Intersection Observer,则简单地将所有的图片加载lazyImages.forEach(function(lazyImage) {lazyImage.src = lazyImage.dataset.src;lazyImage.classList.remove("lazy");});} });
此JavaScript代码使用Intersection Observer API(如果浏览器支持)来观察图片是否在视口中可见。如果图片可见,则将实际图片的URL赋值给
src
属性,并从lazy
类中移除。如果浏览器不支持Intersection Observer,那么它会简单地将所有图片加载出来。 3. 样式调整:为了更好地展示懒加载效果,你可以为占位符图片和实际图片添加一些样式。img {max-width: 100%;height: auto;display: block; } .lazy {filter: blur(5px); /* 可选:模糊效果 */opacity: 0.5; /* 可选:透明度降低 */ }
以上是一种实现懒加载的方法。当页面滚动或重新调整大小时,图片将根据它们在视口中的可见性自动加载。 请注意,懒加载并不局限于图片,你也可以将它应用于其他需要延迟加载的资源,比如视频或音频文件
完整代码
<!DOCTYPE html>
<html>
<head><title>Lazy Load</title><style>img {max-width: 100%;height: auto;display: block;}.lazy {filter: blur(5px); /* 可选:模糊效果 */opacity: 0.5; /* 可选:透明度降低 */}</style>
</head>
<body>
<h1>Lazy Load Example</h1>
<img src="https://preview.qiantucdn.com/58pic/36/28/63/18558PICu3b842hxJc6mW_PIC2018.gif!w1024_new_small" data-src="https://img1.baidu.com/it/u=422078137,1307526884&fm=253&fmt=auto&app=120&f=JPEG?w=1280&h=800" alt="Lazy Load Image" class="lazy">
<img src="https://preview.qiantucdn.com/58pic/36/28/63/18558PICu3b842hxJc6mW_PIC2018.gif!w1024_new_small" data-src="https://img2.baidu.com/it/u=2546424698,318222608&fm=253&fmt=auto&app=138&f=JPEG?w=889&h=500" alt="Lazy Load Image" class="lazy">
<img src="https://preview.qiantucdn.com/58pic/36/28/63/18558PICu3b842hxJc6mW_PIC2018.gif!w1024_new_small" data-src="https://img1.baidu.com/it/u=422078137,1307526884&fm=253&fmt=auto&app=120&f=JPEG?w=1280&h=800" alt="Lazy Load Image" class="lazy">
<img src="https://preview.qiantucdn.com/58pic/36/28/63/18558PICu3b842hxJc6mW_PIC2018.gif!w1024_new_small" data-src="https://img1.baidu.com/it/u=422078137,1307526884&fm=253&fmt=auto&app=120&f=JPEG?w=1280&h=800" alt="Lazy Load Image" class="lazy">
<img src="https://preview.qiantucdn.com/58pic/36/28/63/18558PICu3b842hxJc6mW_PIC2018.gif!w1024_new_small" data-src="https://img2.baidu.com/it/u=2546424698,318222608&fm=253&fmt=auto&app=138&f=JPEG?w=889&h=500" alt="Lazy Load Image" class="lazy">
<img src="https://preview.qiantucdn.com/58pic/36/28/63/18558PICu3b842hxJc6mW_PIC2018.gif!w1024_new_small" data-src="https://img1.baidu.com/it/u=3622442929,3246643478&fm=253&fmt=auto&app=138&f=JPEG?w=889&h=500" alt="Lazy Load Image" class="lazy">
<img src="https://preview.qiantucdn.com/58pic/36/28/63/18558PICu3b842hxJc6mW_PIC2018.gif!w1024_new_small" data-src="https://img1.baidu.com/it/u=422078137,1307526884&fm=253&fmt=auto&app=120&f=JPEG?w=1280&h=800" alt="Lazy Load Image" class="lazy">
<img src="https://preview.qiantucdn.com/58pic/36/28/63/18558PICu3b842hxJc6mW_PIC2018.gif!w1024_new_small" data-src="https://img2.baidu.com/it/u=2546424698,318222608&fm=253&fmt=auto&app=138&f=JPEG?w=889&h=500" alt="Lazy Load Image" class="lazy">
<img src="https://preview.qiantucdn.com/58pic/36/28/63/18558PICu3b842hxJc6mW_PIC2018.gif!w1024_new_small" data-src="https://img2.baidu.com/it/u=2312383180,3750420672&fm=253&fmt=auto&app=120&f=JPEG?w=1280&h=800" alt="Lazy Load Image" class="lazy"><script>document.addEventListener("DOMContentLoaded", function() {var lazyImages = [].slice.call(document.querySelectorAll("img.lazy"));if ("IntersectionObserver" in window) {var lazyImageObserver = new IntersectionObserver(function(entries, observer) {entries.forEach(function(entry) {if (entry.isIntersecting) {var lazyImage = entry.target;lazyImage.src = lazyImage.dataset.src;lazyImage.classList.remove("lazy");lazyImageObserver.unobserve(lazyImage);}});});lazyImages.forEach(function(lazyImage) {lazyImageObserver.observe(lazyImage);});} else {lazyImages.forEach(function(lazyImage) {lazyImage.src = lazyImage.dataset.src;lazyImage.classList.remove("lazy");});}});
</script>
</body>
</html>
实现效果