1 <!doctype html> 2 <html> 3 <head> 4 <meta charset="utf-8"> 5 <title>无标题文档</title> 6 <style type="text/css"> 7 *{ margin:0; padding:0;} 8 body{ height:2000px;} 9 #box{ width:40px; height:40px; display:none; position:fixed; right:30px; bottom:30px; background:#f00;} 10 </style> 11 <script type="text/javascript"> 12 window.onload=function(){ 13 var oBox=document.getElementById("box"); 14 var clientHeight=document.documentElement.clientHeight; 15 var timer=null; 16 var onOff=true; 17 18 window.onscroll=function(){ 19 var osTop=document.documentElement.scrollTop || document.body.scrollTop; 20 21 if(osTop>=clientHeight){ 22 oBox.style.display=‘block‘; 23 }else{ 24 oBox.style.display=‘none‘; 25 }; 26 27 if(!onOff){ 28 clearInterval(timer); 29 }; 30 onOff=false; 31 }; 32 33 oBox.onclick=function(){ 34 35 timer=setInterval(function(){ 36 var osTop=document.documentElement.scrollTop || document.body.scrollTop; 37 var iSpeed= Math.floor(-osTop/6); 38 var i=document.documentElement.scrollTop = document.body.scrollTop = osTop + iSpeed; 39 40 onOff=true; 41 if(osTop ==0){ 42 clearInterval(timer); 43 } 44 },30); 45 }; 46 }; 47 </script> 48 </head> 49 50 <body> 51 <div id="box"></div> 52 </body> 53 </html>