<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.box {
500px;
height: 500px;
border: 1px solid orange;
display: flex;
flex-direction: column;
align-items: center;
overflow: scroll;
}
img {
300px;
height: 300px;
opacity: 0;
transition: opacity .6s linear;
}
.fade{
opacity: 1;
}
</style>
</head>
<body>
<div class="box">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
<img data-src="https://feed-image.baidu.com/0/pic/1f8728565d98b8747c6c9bfcf5bf1982.jpg" alt="" srcset="">
</div>
<script>
let box = document.querySelector('.box') //最外层的容器
let imgs = document.querySelectorAll('img') //要监听的元素
const options = {
root: box, //外层元素
threshold: 0.1
}
function lazyload(target) {
const io = new IntersectionObserver((entries, observer) => {
entries.forEach(entry => {
if (entry.isIntersecting) {
const img = entry.target
const src = img.getAttribute('data-src')
img.setAttribute('src', src)
img.classList.add('fade')
observer.disconnect()
}
})
}, options)
io.observe(target)
}
imgs.forEach(lazyload)
</script>
</body>
</html>