鼠标的位置

链接https://www.quirksmode.org/js/events_properties.html#position

function doSomething（e）{
	var posx = 0;
	var posy = 0;
	if（！e）var e = window.event;
	if（e.pageX || e.pageY）{
		posx = e.pageX;
		posy = e.pageY;
	}
	else if（e.clientX || e.clientY）{
		posx = e.clientX + document.body.scrollLeft
			+ document.documentElement.scrollLeft;
		posy = e.clientY + document.body.scrollTop
			+ document.documentElement.scrollTop;
	}
	// posx和posy包含相对于文档的鼠标位置
	//用这些信息做点什么
}