<body style="height: 3000px;"> <li id="btn-top">回到顶部</li> <style> #btn-top{ position: fixed; bottom: 0px; right: 0px; display: none; } </style> <script> window.onscroll=function(){ var top=document.getElementById("btn-top"); var scrollTop=document.documentElement.scrollTop||document.body.scrollTop;//获取滚动条高度 //console.log(scrollTop); if(scrollTop>1000){ top.style.display='block' }else{ top.style.display='none' } } var top=document.getElementById("btn-top"); top.onclick=function(){ timer=setInterval(function(){ var scrollTop=document.documentElement.scrollTop||document.body.scrollTop;//获取滚动条高度 var ispeed=Math.floor(-scrollTop/6);//速度 if(scrollTop==0){ clearInterval(timer); } document.documentElement.scrollTop=document.body.scrollTop=scrollTop+ispeed; },30) }; </script>