1.通过css实现：
为页面顶部如body或者自己设置的盒子等加上唯一id属性
<body id="id">
....
<a href="#id">返回顶部</a>
2.js实现
通过设置标签滚动位置判断
document.body.scrollTop=0;
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
.cs_top{
position: fixed;
right: 10px;
bottom: 10px;
height: 60px;
width: 60px;
background-color: darkgray;
opacity: 0.5;
}
.js_top{
position: fixed;
right: 10px;
bottom: 120px;
height: 60px;
width: 60px;
background-color: rebeccapurple;
opacity: 0.5;
}
.hide{
display: none;
}
#content{
height:960px;
width: 100%;
}
#content:before{
content: 'top';
display: block;
}
body:after{
content: 'end';
display: block;
}
</style>
<script> </script>
</head>
<body onscroll="Func();">
<div id="content">
<p>fdffa</p>
<p>fdffa</p>
<p>fdffa</p>
<p>fdffa</p>
<p>fdffa</p>
<p>fdffa</p>
<p>fdffa</p>
<p>fdffa</p>
<p>fdffa</p>
</div>
<div class="cs_top">
<a href="#content">返回顶部</a>
</div>
<div class="js_top hide">
<a href="javascript:void(0);" onclick="GoTop();">返回顶部</a>
</div>
</body>
</html>
<script src="../02js拾遗/jquery.js"></script>
<script>
function Func(){
var scrollTop=document.body.scrollTop;
var ele=document.getElementsByClassName('js_top')[0];
if (scrollTop>50){
ele.classList.remove('hide');
}else{
ele.classList.add('hide');
}
} function GoTop(){
document.body.scrollTop=0;
} </script>