var timeout      = 500;
var closeTimer   = 0;
var dropDownMenu = 0;

function menuOpen(id)
{   
  
    menuCancelTimeout();

    if(dropDownMenu) dropDownMenu.style.visibility = 'hidden';

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

}

function menuClose()
{
    if(dropDownMenu) dropDownMenu.style.visibility = 'hidden';
}


function menuCloseTimeout()
{
    closeTimer = window.setTimeout(menuClose, timeout);
}


function menuCancelTimeout()
{
    if(closeTimer)
    {
        window.clearTimeout(closeTimer);
        closeTimer = null;
    }
}


document.onclick = menuClose;