一个小小的返回顶部
废话不多说上码：
<!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>
.topBn{
width:50px;
height: 50px;
font-size: 40px;
line-height: 60px;
border:1px solid #000000;
text-align: center;
box-shadow: 2px 2px 2px 2px #CCCCCC;
transition: all 0.5s;
outline: 1px solid #000000;
outline-offset: 0px;
position: fixed;
bottom: 100px;
right: 100px;
display: none;
}
.topBn:hover
{
outline-offset: 20px;
}
</style>
</head>
<body>
<div class="topBn">^</div>
<img src="./img/a.png">
<img src="./img/b.png">
<img src="./img/c.png">
<img src="./img/d.png">
<img src="./img/e.png">
<img src="./img/a.png">
<img src="./img/b.png">
<img src="./img/c.png">
<img src="./img/d.png">
<img src="./img/e.png">
<img src="./img/a.png">
<img src="./img/b.png">
<img src="./img/c.png">
<img src="./img/d.png">
<img src="./img/e.png">
<img src="./img/a.png">
<img src="./img/b.png">
<img src="./img/c.png">
<img src="./img/d.png">
<img src="./img/e.png">
<script>
var topBn;
var bool=false;
init();
function init(){
topBn=document.querySelector(".topBn");
topBn.onclick=clickHandler;
window.onscroll=scrollHandler;
setInterval(enterFrame,16);
}
function clickHandler(){
bool=true;
}
function scrollHandler(){
if(document.documentElement.scrollTop>document.documentElement.clientHeight){
topBn.style.display="block"
}else{
topBn.style.display="none";
}
}
function enterFrame(){
if(!bool) return;
document.documentElement.scrollTop-=100;
if(document.documentElement.scrollTop===0){
bool=false;
}
}
</script>
</body>
</html>
点击效果图
