title: Unable to migrate extjs 3 to extjs 4
body: <p>I am migrating from extjs version 3 to extjs version 4. I have added the compatibility layer to my project using Ext 3 to 4 Migration Guide given by sencha.<br>
  To enable Ext 3 compatibility I included the following lines after ext-all-debug.js(extjs4).
        //compatiblity
        
        </p>
  
  <p>I removed </p>
  
  <pre><code>  // Ext 3
    &lt;script type="text/javascript" src="ext/adapter/ext/ext-base.js"&gt;&lt;/script&gt;
    &lt;script type="text/javascript" src="scripts/external/extjs/ext-all.js"&gt;&lt;/script&gt;
  </code></pre>
  
  <p>I fixed below script error</p>
  
  <pre><code>  // Ext 3:
    Ext.reg('mycoolclass', Ext.ux.MyCoolClass);
  
    // Ext 4 (compatibility mode only, optional)
       Ext.reg('mycoolclass', 'Ext.ux.MyCoolClass');
  </code></pre>
  
  <p>Still getting following error in extjs-all-debug.js.</p>
  
  <pre><code>    TypeError: me.events is undefined
             event = me.events[ename];
  </code></pre>
  
  <p>what I am doing wrong ?
  How to avoid this kind of error ?
  Please anyone suggest to migrate existing extjs3 application to extjs4 with minimal code change</p>