性能优化案例之懒加载

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<img src="./loading.gif" data-src="./img1.jpg" alt="" height="300">
<img src="./loading.gif" data-src="./img1.jpg" alt="" height="300">
<img src="./loading.gif" data-src="./img1.jpg" alt="" height="300">
<img src="./loading.gif" data-src="./img1.jpg" alt="">
<img src="./loading.gif" data-src="./img1.jpg" alt="">
<img src="./loading.gif" data-src="./img1.jpg" alt="">
<img src="./loading.gif" data-src="./img1.jpg" alt="">
<img src="./loading.gif" data-src="./img1.jpg" alt="">
<img src="./loading.gif" data-src="./img1.jpg" alt="">
<img src="./loading.gif" data-src="./img1.jpg" alt="">
<img src="./loading.gif" data-src="./img1.jpg" alt="">


<script>
const img = document.getElementsByTagName('img');
const len = img.length

let n = 0;
const lazyLoad = ()=>{
let {clientHeight} = document.documentElement
let scrollTop = document.documentElement.scrollTop || document.body.scrollTop
for(let i = n ; i<len ; i++){
console.log(img[i].offsetTop)
if(img[i].offsetTop < clientHeight+scrollTop ){
img[i].src = img[i].getAttribute("data-src")
n = i+1
}
}
}
lazyLoad()
window.onscroll = lazyLoad
 
</script>
</body>
</html>

 

posted @ 2023-03-29 15:04  蜗牛般庄  阅读(11)  评论(0编辑  收藏  举报
Title
页脚 HTML 代码