封装鼠标拖拽事件

function drag(){
	var x,
		y;
	addEvent(elem,'mousedown',function(e){
		var e =  e || window.event;
		x = pagePos(e).X - getStyles(elem,'left')；
		y = pagePos(e).Y - getStyele(elem,'top');

		addEvent(document,'mousemove',mousemove);
		addEvent(document,'mouseup',mouseup);
		cancelBubble(e);
		preventDefaultEvent(e);
	});
	function mousemove(e){
		var e = e || window.event;
		elem.style.left = pagePos(e).X - x +'px'；
		elem.style.top = pagePose(e)Y - y + 'px'
	}
	function mouseup(e){
		var e = e || window.event
		removeEvent(document,'mousemove',mouseMove);
		removeEvent(document,'mouseup',mouseUp);
	}
}
drag();