javascript获取元素结点到页面的绝对距离的方式

var div = document.getElementById('div');
var p = getPos(div);

function getPos(obj) {

    var pos = {left:0,top:0};

    while(obj) {
        pos.left += obj.offsetLeft;
        pos.top += obj.offsetTop;
        obj = obj.offsetParent;
    }
    return pos;
}

<div id="div" style="width:50px; height:50px; background:yellow; margin:50px 0 0 50px;"></div>