title: ExtJs select component by id starting with a string
body: <p>i need to create a component dynamically by a button click. My restrictions are:</p>
  
  <ol>
  <li>It's going to has an Id starts with a fixed string like 'myComp_' and followed by a random number</li>
  <li>At any time there will be only one component that has an id starts with 'myComp_xxx'</li>
  </ol>
  
  <p>So before creating the component i have to check if there's any created before and remove it... My problem starts here. Ext.getCmp() wants the specific id. But i only have that fixed string : myComp_...</p>
  
  <p>Is there any way to get the component created before???</p>
  
  <p>Thanks in advance and sorry about my English.</p>