var nav_timeout = 500;
var nav_closetimer = 0;
var nav_ddmenuitem = 0;

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

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

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

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

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

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

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