Can't add a menu item on ExtJS 3.4

Can't add a menu item on ExtJS 3.4

I'm trying the following code to add a menu item at runtime but I can't
get it to work, the ExtJS documentation has samples only to create the
entire menu along with the menu item. Any help is much appreciated.
var menuItem = Ext.create('Ext.menu.Item', { text: 'menu item'});
Error:
TypeError: b[e] is not a constructor
Ext.ComponentMgr.create()ext.axd?v=31893 (line 7)
()debugg...al code (line 2)
...;if(a.getMonth()==G.getMonth()&&a.getFullYear()==G.getFullYear()){this.cells.rem...