
php实现图片延时加载的方法:在到达指定加载图片位置时,用data-src属性值替换img的src属性值即可,如【imgs[i].src = imgs[i].getAttribute('data-src');】。

在到达指定加载图片位置时,用data-src的属性值替换img的src的属性值即可,这个时候img就会去请求资源。
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imgs[i].src = imgs[i].getAttribute('data-src');代码实现:
<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <meta http-equiv="X-UA-Compatible" content="ie=edge">
 <title>图片懒加载</title>
 <style>
 img {
 display: block;
 width: 100%;
 height: 300px;
 margin-bottom: 20px;
 }
 </style>
</head>
<body>
 <img data-src="./images/1.jpg" alt="">
 <img data-src="./images/2.jpg" alt="">
 <img data-src="./images/3.jpg" alt="">
 <img data-src="./images/4.jpg" alt="">
 <img data-src="./images/5.jpg" alt="">
 <img data-src="./images/6.jpg" alt="">
 <img data-src="./images/7.jpg" alt="">
 <img data-src="./images/8.jpg" alt="">
 <img data-src="./images/9.jpg" alt="">
 <img data-src="./images/10.jpg" alt="">
 <img data-src="./images/1.jpg" alt="">
 <img data-src="./images/2.jpg" alt="">
</body>
<script>
 var imgs = document.querySelectorAll('img');
 //offsetTop是元素与offsetParent的距离,循环获取直到页面顶部
 function getTop(e) {
 var T = e.offsetTop;
 while(e = e.offsetParent) {
 T += e.offsetTop;
 }
 return T;
 }
 function lazyLoad(imgs) {
 var H = document.documentElement.clientHeight;//获取可视区域高度
 var S = document.documentElement.scrollTop || document.body.scrollTop;
 for (var i = 0; i < imgs.length; i++) {
 if (H + S > getTop(imgs[i])) {
 imgs[i].src = imgs[i].getAttribute('data-src');
 }
 }
 }
 window.onload = window.onscroll = function () { //onscroll()在滚动条滚动的时候触发
 lazyLoad(imgs);
 }
</script>
</html>