title: Ext JS: what is xtype good for?
body: <p>I see there are lot's of examples in Ext JS where instead of actually creating Ext JS objects, an object literal with an <code>xtype</code> property is passed in.</p>
  
  <p>What is this good for? Where is the performance gain (if that's the reason) if the object is going to be created anyway?</p>