获取元素在浏览器中的绝对位置（从jquery1.8中抠出来）

<style>
html,body{margin:0;padding:0;}
.d1{margin-left:40px;background:red;width:2000px;height:100px;position:relative;}
.d2{margin-left:40px;background:blue;width:1000px;height:80px;}
</style><div id="d1" class="d1">
<div id="d2" class="d2"></div>
</div>

function getWindow( elem ) {
return mylibs.isWindow( elem ) ?
elem :
elem.nodeType === 9 ?
elem.defaultView || elem.parentWindow :
false;
};var mylibs = {
isWindow: function( obj ) {
return obj != null && obj == obj.window;
},
//获取元素在浏览器中的绝对位置
offset:function(elem){
var docElem, win, clientTop, clientLeft, scrollTop, scrollLeft,
box = { top: 0, left: 0 },
doc = elem && elem.ownerDocument; if ( !doc ) {
return;
} docElem = doc.documentElement;
//黑莓5 ios3(iphoe) 没有getBoundingClientRect
if ( typeof elem.getBoundingClientRect !== "undefined" ) {
box = elem.getBoundingClientRect();
}
win = getWindow( doc ); clientTop = docElem.clientTop || document.body.clientTop || 0;
clientLeft = docElem.clientLeft || document.body.clientLeft || 0;
scrollTop = win.pageYOffset || docElem.scrollTop;
scrollLeft = win.pageXOffset || docElem.scrollLeft;
return {
top: box.top + scrollTop - clientTop,
left: box.left + scrollLeft - clientLeft
};
}
};//调用：
document.getElementById('d2').onclick = function(){
alert(mylibs.offset(this).left);
};