var currentmenu = 0;
document.onclick = hidemenu; 

function showmenu(id) {
        if (currentmenu) {
            currentmenu.style.visibility = 'hidden';
        }
        currentmenu = document.getElementById(id);
        if (currentmenu) {
            currentmenu.style.visibility = 'visible';
        }
    }
function hidemenu() {
    if (currentmenu) 
        { currentmenu.style.visibility = 'hidden'; }
}