<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>返回顶部</title> <style> body{ height: 3000px; } #box{ height: 80px; width: 30px; background: orange; border:1px red solid; cursor: pointer; position:fixed; bottom: 50px; right: 50px; display: none; } </style> </head> <body> <div id="box">返回顶部</div> </body> <script> var oBox = document.getElementById("box"); var speed = 10; var time = null; window.onscroll = function(){ var Top = document.documentElement.scrollTop ||document.body.scrollTop; if (Top<=0) { clearInterval(time); }; if (Top>300) { oBox.style.display = "block"; }else{ oBox.style.display = "none"; }; } oBox.onclick=function(){ time = setInterval(move,1) function move(){ document.body.scrollTop -= speed; document.documentElement.scrollTop-= speed; //console.log(document.body.scrollTop) } } </script> </html>
原文：http://www.cnblogs.com/jakning/p/4241854.html