<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<style>
img {
display: block;
margin-bottom: 50px;
width: 400px;
height: 400px;
}
</style>
</head>
<body>
<img src="./img/default.JPG" data-src="./img/new.JPG" alt="">
<img src="./img/default.JPG" data-src="./img/new.JPG" alt="">
<img src="./img/default.JPG" data-src="./img/new.JPG" alt="">
<img src="./img/default.JPG" data-src="./img/new.JPG" alt="">
<img src="./img/default.JPG" data-src="./img/new.JPG" alt="">
<img src="./img/default.JPG" data-src="./img/new.JPG" alt="">
<img src="./img/default.JPG" data-src="./img/new.JPG" alt="">
<img src="./img/default.JPG" data-src="./img/new.JPG" alt="">
<img src="./img/default.JPG" data-src="./img/new.JPG" alt="">
<img src="./img/default.JPG" data-src="./img/new.JPG" alt="">
<img src="./img/default.JPG" data-src="./img/new.JPG" alt="">
<script>
let num = document.getElementsByTagName('img').length;
let img = document.getElementsByTagName("img");
let n = 0; //存储图片加载到的位置，避免每次都从第一张图片开始遍历
lazyload(); //页面载入完毕加载可是区域内的图片
window.onscroll = lazyload;
function lazyload() { //监听页面滚动事件
let seeHeight = document.documentElement.clientHeight; //可见区域高度
let scrollTop = document.documentElement.scrollTop || document.body.scrollTop; //滚动条距离顶部高度
for (let i = n; i < num; i++) {
if (img[i].offsetTop < seeHeight + scrollTop) {
if (img[i].getAttribute("src") == "./img/default.JPG") {
img[i].src = img[i].getAttribute("data-src");
}
n = i + 1;
}
}
}
</script>
</body>
</html>
