title: Create new instance of extended element
body: <p>I am using extjs 3.4</p>
  
  <p>I have an element:</p>
  
  <pre><code>App.Components.ComboBox = Ext.extend(Ext.form.ComboBox, {
      constructor: function (config) {
  
          config = Ext.apply({
              triggerAction: 'all',
              mode: 'local',
              editable: true,
              lastQuery: '',
              forceSelection: true
          }, config);
  
          App.Components.ComboBox.superclass.constructor.call(this, config);
      }    //other methods ommited
  });
  Ext.reg('appcombo', App.Components.ComboBox);
  </code></pre>
  
  <p>I would like to create this element dynamically and load it's store.</p>
  
  <p>I know I can create ComboBox with:</p>
  
  <pre><code>var newCB = Ext.form.ComboBox(config);
  </code></pre>
  
  <p>But how to create new element of type appcombo?</p>