title: EXTJS fireEvent
body: <p>In the Ext.panel component, there is an event called expand(Ext.panel p). </p>
  
  <p>Now I have 2 panels, A and B. The requirement is both of them should expand and collapse together. So when I expand A, i somehow need to fire the 'expand' event for B also. That should in turn fire the event handler for B.
  So the syntax (please help me with this):</p>
  
  <pre><code>A.on('expand', userPanelExpand)//event handler for A that performs some logic
  </code></pre>
  
  <p>Now how can I add a fireEvent('expand') for B? Should it read:  </p>
  
  <pre><code>A.on('expand', userPanelExpand);
  function userPanelExpand(){
  //some logic
  this.fireEvent('expand', this.B);
  }
  </code></pre>
  
  <p>Something not right here.I get Stackvoerflow error at the last line.</p>