JavaScript 未知高度元素垂直居中实现代码

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>JavaScript未知高度元素的垂直居中的方法</title> <script type="text/javascript"> function vMiddle(){ var middleDiv=document.getElementById("wrap"); var divHeight=middleDiv.offsetHeight; var bodyHeight=document.body.offsetHeight ; if(bodyHeight>divHeight) middleDiv.style.marginTop=-divHeight/2+"px"; else{ middleDiv.style.marginTop=0; middleDiv.style.top=0; } } </script> <style type="text/css"> html,body{height:100%;padding:0;margin:0;} #wrap{width:800px;margin:0 auto;border:1px solid red;position:absolute;top:50%;left:50%;margin-left:-400px;} </style> </head> <body onload="vMiddle();"> Jb51.net<br> 脚本之家<br> </body> </html>
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