var dropDownMenuItem = 0;

function openMenu(id) {
    if (dropDownMenuItem) {
        dropDownMenuItem.style.visibility = 'hidden';
    }

    dropDownMenuItem = document.getElementById(id);
    dropDownMenuItem.style.visibility = 'visible';
}

function closeMenu() {
    if (dropDownMenuItem) {
        dropDownMenuItem.style.visibility = "hidden";
    }
}

document.onclick = closeMenu;