var menus = ['submenu-1', 'submenu-2', 'submenu-3', 'submenu-4'];

function toggleMenu(id) {
	for (var i = 0; i < menus.length; i++) {
		var menu = document.getElementById(menus[i]);

		if (menus[i] != id && menu) {
			menu.style.visibility = 'hidden';
		}
	}

	var menu = document.getElementById(id);

	if (menu) {
		if (menu.style.visibility != 'visible') {
			menu.style.visibility = 'visible';
		}
		else {
			menu.style.visibility = 'hidden';
		}
	}

	return false;
}