JavaScriptマウス座標の取得方法

x  : <input id=pX name="pX" type=text >
y  : <input id=pY name="pY" type=text >
function mouseMove(ev) 
{ 
	ev= ev || window.event; 
	var mousePos = mouseCoords(ev); 
	//alert(ev.pageX); 
	document.getElementById("pX").value = mousePos.x; 
	document.getElementById("pY").value = mousePos.y; 
} 

function mouseCoords(ev) 
{ 
	if(ev.pageX || ev.pageY){ 
		return {x:ev.pageX, y:ev.pageY}; 
	} 
	return { 
	x:ev.clientX + document.body.scrollLeft - document.body.clientLeft, 
	y:ev.clientY + document.body.scrollTop - document.body.clientTop 
	}; 
} 

document.onmousemove = mouseMove;