jquery函数:网页弹出层完美居中的函数

showDiv($("#pop"));
function showDiv(obj){
$(obj).show();
center(obj);
$(window).scroll(function(){
center(obj);
});
$(window).resize(function(){
center(obj);
});
}

function center(obj){
var windowWidth = document.documentElement.clientWidth;
var windowHeight = document.documentElement.clientHeight;
var popupHeight = $(obj).height();
var popupWidth = $(obj).width();
$(obj).css({
"position": "absolute",
"top": (windowHeight-popupHeight)/2+$(document).scrollTop(),
"left": (windowWidth-popupWidth)/2
});
}