The source code

    /**
     * @class Ext.menu.MenuMgr
     * Provides a common registry of all menu items on a page so that they can be easily accessed by id.
     * @singleton
     */
    Ext.menu.MenuMgr = function(){
       var menus,
           active,
           map,
           groups = {},
           attached = false,
           lastShow = new Date();

       // private - called when first menu is created
       function init(){
           menus = {};
           active = new Ext.util.MixedCollection();
           map = Ext.getDoc().addKeyListener(27, hideAll);
           map.disable();
       }

       // private
       function hideAll(){
           if(active && active.length > 0){
               var c = active.clone();
               c.each(function(m){
                   m.hide();
               });
               return true;
           }
           return false;
       }

       // private
       function onHide(m){
           active.remove(m);
           if(active.length < 1){
               map.disable();
               Ext.getDoc().un("mousedown", onMouseDown);
               attached = false;
           }
       }

       // private
       function onShow(m){
           var last = active.last();
           lastShow = new Date();
           active.add(m);
           if(!attached){
               map.enable();
               Ext.getDoc().on("mousedown", onMouseDown);
               attached = true;
           }
           if(m.parentMenu){
              m.getEl().setZIndex(parseInt(m.parentMenu.getEl().getStyle("z-index"), 10) + 3);
              m.parentMenu.activeChild = m;
           }else if(last && !last.isDestroyed && last.isVisible()){
              m.getEl().setZIndex(parseInt(last.getEl().getStyle("z-index"), 10) + 3);
           }
       }

       // private
       function onBeforeHide(m){
           if(m.activeChild){
               m.activeChild.hide();
           }
           if(m.autoHideTimer){
               clearTimeout(m.autoHideTimer);
               delete m.autoHideTimer;
           }
       }

       // private
       function onBeforeShow(m){
           var pm = m.parentMenu;
           if(!pm && !m.allowOtherMenus){
               hideAll();
           }else if(pm && pm.activeChild){
               pm.activeChild.hide();
           }
       }

       // private
       function onMouseDown(e){
           if(lastShow.getElapsed() > 50 && active.length > 0 && !e.getTarget(".x-menu")){
               hideAll();
           }
       }

       return {

           /**
            * Hides all menus that are currently visible
            * @return {Boolean} success True if any active menus were hidden.
            */
           hideAll : function(){
                return hideAll();
           },

           // private
           register : function(menu){
               if(!menus){
                   init();
               }
               menus[menu.id] = menu;
               menu.on({
                   beforehide: onBeforeHide,
                   hide: onHide,
                   beforeshow: onBeforeShow,
                   show: onShow
               });
           },

            /**
             * Returns a {@link Ext.menu.Menu} object
             * @param {String/Object} menu The string menu id, an existing menu object reference, or a Menu config that will
             * be used to generate and return a new Menu instance.
             * @return {Ext.menu.Menu} The specified menu, or null if none are found
             */
           get : function(menu){
               if(typeof menu == "string"){ // menu id
                   if(!menus){  // not initialized, no menus to return
                       return null;
                   }
                   return menus[menu];
               }else if(menu.events){  // menu instance
                   return menu;
               }else if(typeof menu.length == 'number'){ // array of menu items?
                   return new Ext.menu.Menu({items:menu});
               }else{ // otherwise, must be a config
                   return Ext.create(menu, 'menu');
               }
           },

           // private
           unregister : function(menu){
               delete menus[menu.id];
               menu.un("beforehide", onBeforeHide);
               menu.un("hide", onHide);
               menu.un("beforeshow", onBeforeShow);
               menu.un("show", onShow);
           },

           // private
           registerCheckable : function(menuItem){
               var g = menuItem.group;
               if(g){
                   if(!groups[g]){
                       groups[g] = [];
                   }
                   groups[g].push(menuItem);
               }
           },

           // private
           unregisterCheckable : function(menuItem){
               var g = menuItem.group;
               if(g){
                   groups[g].remove(menuItem);
               }
           },

           // private
           onCheckChange: function(item, state){
               if(item.group && state){
                   var group = groups[item.group],
                       i = 0,
                       len = group.length,
                       current;

                   for(; i < len; i++){
                       current = group[i];
                       if(current != item){
                           current.setChecked(false);
                       }
                   }
               }
           },

           getCheckedItem : function(groupId){
               var g = groups[groupId];
               if(g){
                   for(var i = 0, l = g.length; i < l; i++){
                       if(g[i].checked){
                           return g[i];
                       }
                   }
               }
               return null;
           },

           setCheckedItem : function(groupId, itemId){
               var g = groups[groupId];
               if(g){
                   for(var i = 0, l = g.length; i < l; i++){
                       if(g[i].id == itemId){
                           g[i].setChecked(true);
                       }
                   }
               }
               return null;
           }
       };
    }();