function AppMenu() {
  var self = this;
  var _app_menu_selector;
  var _app_menu_mbreite;
  var _app_menu_url_prefix = "";
  var _app_menu_template;

  /*
   * die nachfolgenden Funktionen steuern das ein- und
   * ausblenden des menues
   */
  this.init = function (url_prefix, mdesc, mtpl, mselector, mbreite) {
    self._app_menu_selector = mselector;
    self._app_menu_mbreite = mbreite;
    /*document.querySelector( "#nav-toggle" ).addEventListener("click", function() {
      app_menu_toggle();
    });*/
    var menu = document.querySelector(self._app_menu_selector);
    menu.style.flexBasis = '0em';
    self._app_menu_url_prefix = url_prefix;

    var request = new XMLHttpRequest();
    request.open("GET", mtpl);
    request.addEventListener('load', function(event) {
       if (request.status >= 200 && request.status < 300) {
          //console.log(request.responseText);
          self._app_menu_template = request.responseText;
          Mustache.parse(self._app_menu_template);   // optional, speeds up future uses
          var menuDiv = document.createElement("div");
          menuDiv.classList.add('app-menu-content');
          menuDiv.style.position = 'relative';
          menuDiv.style.left = '-300px';
          menuDiv.style.right = '0px';
          menu.appendChild(menuDiv);

          self.app_menu_laden(mdesc);
       } else {
          console.warn(request.statusText, request.responseText);
       }
    });
    request.send();

  };

  this.app_menu_do_toggle = function(elem) {
    self.toggle();
  };

  this.toggle = function() {
    var menuDiv = document.querySelector(self._app_menu_selector);
    if(menuDiv.classList.contains('app-menu-open')) {
      menuDiv.classList.remove('app-menu-open');
      menuDiv.style.flexBasis = '0em';
    } else {
      menuDiv.classList.add('app-menu-open');
      menuDiv.style.flexBasis = self._app_menu_mbreite;
    }
  };

  /*
   * ab hier Steuerung des Menueinhalts
   */


  /*
   * mdesc: der URL einer JSON-Datei mit einer Menuebeschreibung
   */
  this.app_menu_laden = function(mdesc, richtung) {
    var xmlhttp = new XMLHttpRequest();
    var url = self._app_menu_url_prefix + mdesc;
    xmlhttp.onreadystatechange = function() {
      if (this.readyState == 4 && this.status == 200) {
        self.app_menu_bauen(JSON.parse(this.responseText), richtung);
      }
    };
    xmlhttp.open("GET", url, true);
    xmlhttp.send();
  };

  this.app_menu_bauen = function(menuejs, richtung) {
    var menuDiv = document.createElement("div");
    menuDiv.classList.add('app-menu-content');
    menuDiv.style.position = 'relative';
    menuDiv.innerHTML = Mustache.render(self._app_menu_template, menuejs);

    self.app_menu_remove_event_listener_multi('.smenu', 'click', self.app_menu_klick_herunter);
    self.app_menu_remove_event_listener_multi('.bitem', 'click', self.app_menu_klick_herauf);
    self.app_menu_remove_event_listener_multi('.mitem', 'click', self.app_menu_ausfuehren);

    var menu = document.querySelector(self._app_menu_selector);
    menu.innerHTML = '';
    menu.append(menuDiv);

    self.app_menu_add_event_listener_multi('.smenu', 'click', self.app_menu_klick_herunter);
    self.app_menu_add_event_listener_multi('.bitem', 'click', self.app_menu_klick_herauf);
    self.app_menu_add_event_listener_multi('.mitem', 'click', self.app_menu_ausfuehren);
  };

  this.app_menu_klick_herunter = function() {
    self.app_menu_laden(this.getAttribute('data-verweis'), 'herunter');
  };

  this.app_menu_klick_herauf = function() {
    self.app_menu_laden(this.getAttribute('data-verweis'), 'herauf');
  };

  this.app_menu_ausfuehren = function() {
    var functionName = this.getAttribute('data-verweis');
    eval(functionName + "(this)");
  };

  /* --- Helferlein ---*/
  /*
    sel - '.smenu'
    evt - 'click' fuer onclick
    func - der verweis auf die funktion
  */
  this.app_menu_remove_event_listener_multi = function(sel, evt, func) {
    var elem = document.querySelectorAll(sel);
    for (var index = 0; index < elem.length; index++) {
      elem[index].removeEventListener(evt, func);
    }
  };

  this.app_menu_add_event_listener_multi = function(sel, evt, func) {
    var elem = document.querySelectorAll(sel);
    for (var index = 0; index < elem.length; index++) {
      elem[index].addEventListener(evt, func);
    }
  };
}