获取元素相的坐标

所有现代浏览器均支持以下3个属性:offsetParent,offsetLeft,offsetTop
不同点在于有的浏览器的offsetParent是直接指向根节点的，有的不是

function pageX(elem){
        //查看是否位于根元素
	return elem.offsetParent?elem.offsetLeft + pageX(elem.offsetParent):elem.offsetLeft;
}

function pageY(elem){
	return elem.offsetParent?elem.offsetTop + pageY(elem.offsetParent):elem.offsetTop;
}

获取相对于父元素的位置

function parentX(elem){
	return elem.parentNode == elem.offsetParent?elem.offsetLeft:pageX(elem)-pageX(elem.parentNode);
}

function parentY(elem){
	return elem.parentNode == elem.offsetParent?elem.offsetTop:pageY(elem)-pageY(elem.parentNode);
}

获取相对于CSS容器的位置

function cssX(elem){
	return parseInt(getStyle(elem,"left"));
}
function cssY(elem){
	return parseInt(getStyle(elem,"top"));
}

获取隐藏元素的高度

//获取隐藏元素的高度和宽度
	function fullHeight(elem) {
		if(getStyle(elem,"display") != "none") {
			return elem.offsetHeight || getHeight(elem);
		}
		var old = resetCss(elem, {
			display:"",
			visibility:"hidden",
			position:"absolute"
		});
		var h = elem.offsetHeight || getHeight(elem);
		restoreCss(elem,old);
		return h;
	}

	function resetCss(elem,prop) {
		var old = {};
		for(var i in prop) {
			old[i] = elem.style[i];
			elem.style[i] = prop[i];
		}
		return old;
	}

	function restoreCss(elem,old) {
		for(var i in prop) {
			elem.style[i] = old[i];
		}
	}