<!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>
<style>
* {
margin: 0px;
padding: 0px;
}
div:first-child {
width: 100%;
height: 200px;
background: pink;
}
div:nth-child(2) {
width: 100%;
height: 400px;
background: green;
}
div:nth-child(3) {
width: 100%;
height: 400px;
background: blue;
}
div:nth-child(4) {
width: 100%;
height: 200px;
background: red;
}
.box {
background: peru;
width: 20px;
height: 50px;
position: absolute;
top: 200px;
right: 0px;
}
.jay {
position: relative;
}
</style>
</head>
<body>
<div class="jay">
<div>
我是head
</div>
<div>
我是banner
</div>
<div>
我是Body
</div>
<div>
我是footer
</div>
<div class="box">
</div>
</div>
<script>
var box = document.querySelector('.box')
window.onscroll = function () {
// console.log(document.documentElement.scrollTop);
var flag = window.pageYOffset
console.log(flag);
if (flag >= 200) {
box.style.position = 'fixed'
console.log(111);
box.style.top = '0px'
} else {
box.style.position = 'absolute'
box.style.top = '200px'
}
}
</script>
</body>
</html>