var timeout    = 500;
var closetimer = 0;
var ddmenuitem = 0;

// open hidden layer
function mopen(id) {
  // cancel close timer
  mcancelclosetime();

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

  // get new layer and show it
  ddmenuitem = document.getElementById(id);
  ddmenuitem.style.visibility = 'visible';
}

// close showed layer
function mclose() {
  if(ddmenuitem) ddmenuitem.style.visibility = 'hidden';
}

// go close timer
function mclosetime() {
  closetimer = window.setTimeout(mclose, timeout);
}

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

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