/* Displays a submenu */
function display_submenu(menu_id) {
    var element = document.getElementById("book-options-" + menu_id);
    element.className = 'book-options visible';
}

/* Hides a submenu */
function hide_submenu(menu_id) {
    var element = document.getElementById("book-options-" + menu_id);
    element.className = 'book-options hidden';
}

/* Displays the active menu div and it hides the passive menu div */
function display_active_state(menu_id) {
	var element = document.getElementById("menu-active-" + menu_id);
	element.className = 'stat book-main-submenu visible';
	element = document.getElementById("menu-passive-" + menu_id);
    element.className = 'stat book-main-submenu hidden';
}

/* Displays the passive menu div and it hides the active menu div */
function hide_active_state(menu_id) {
	var element = document.getElementById("menu-active-" + menu_id);
    element.className = 'stat book-main-submenu hidden'; 
	element = document.getElementById("menu-passive-" + menu_id);
    element.className = 'stat book-main-submenu visible';
}