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html懒人加载实现

news 2025/8/1 16:20:26

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

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