页面向上向下滚动，分享到的模块随着滑动。
要点：
复制代码 代码如下:
var scrtop =document.documentElement.scrollTop||document.body.scrollTop;
var height = document.documentElement.clientHeight||document.body.clientHeight;
var top = scrtop + (height - jb51.offsetHeight)/2;
top = parseInt(top);
获得页面垂直居中的位置
上代码：
<!DOCTYPE html> <html> <head> <meta charset="gb2312" /> <title>无标题文档</title> <style> body{margin:0; padding:0; font:12px/1.5 arial; height:2000px;} #jb51{width:100px; height:200px; line-height:200px; text-align:center; border:1p solid #ccc; background:#f5f5f5; position:absolute; left:-100px; top:0;} #jb51_tit{position:absolute; right:-20px; top:60px; width:20px; height:60px; padding:10px 0; background:#06c; text-align:center; line-height:18px; color:#fff;} </style> <script> window.onload = function(){ var jb51 = document.getElementById("jb51"); jb51.onmouseover = function(){ startrun(jb51,0,"left") } jb51.onmouseout = function(){ startrun(jb51,-100,"left") } window.onscroll = window.onresize = function(){ var scrtop=document.documentElement.scrollTop||document.body.scrollTop; var height=document.documentElement.clientHeight||document.body.clientHeight; var top = scrtop + (height - jb51.offsetHeight)/2; top = parseInt(top); startrun(jb51,top,"top") } } var timer = null function startrun(obj,target,direction){ clearInterval(timer); timer = setInterval(function(){ var speed = 0; if(direction == "left"){ speed = (target-obj.offsetLeft)/8; speed = speed>0?Math.ceil(speed):Math.floor(speed); if(obj.offsetLeft == target){ clearInterval(timer); }else{ obj.style.left = obj.offsetLeft + speed + "px"; } } if(direction == "top"){ speed = (target-obj.offsetTop)/8; speed = speed>0?Math.ceil(speed):Math.floor(speed); if(obj.offsetTop == target){ clearInterval(timer); }else{ obj.style.top = obj.offsetTop + speed + "px"; } document.title = obj.offsetTop + ',' + target + ',' +speed; } },30) } </script> </head> <body> <div> 分享到内容 <span>分享到</span> </div> </body> </html>