var timeout = 500;
var closetimer = 0;
var menuById = 0;

function showmenu(obj) {
   // cancel close timer
	menuCancelCloseTime();

	// close old layer
	if(menuById) menuById.style.visibility = 'hidden';

	// get new layer and show it
	menuById = document.getElementById(obj);
	menuById.style.visibility = 'visible';
}
function hidemenu() {
	if(menuById) {
	   menuById.style.visibility = 'hidden';
	}
}
function menuCloseTime() {
	closetimer = window.setTimeout(hidemenu, timeout);
}

// cancel close timer
function menuCancelCloseTime() {
	if(closetimer){
		window.clearTimeout(closetimer);
		closetimer = null;
	}
}

// close layer when click-out
document.onclick = hidemenu;