title: div.appendChild(div) equivalent in ExtJS4
body: <p>I am transitioning my code to ExtJs4.1.1.
  In one part of the code I have used Javascript's <code>appendChild()</code> method to add new <code>div</code> elements to an existing <code>div</code> container.</p>
  
  <p>I want this to be done in ExtJs now.</p>
  
  <p><strong>Existing code:</strong></p>
  
  <pre><code>var container = document.getElementById('treeContainer');
  var nodeDiv = document.createElement("div");
  
  // nodeDiv related code... setting properties and attributes
  nodeDiv.innerHTML = "&lt;div class='NodeContent'&gt;" + node.displayText + "&lt;/div&gt;";
  nodeDiv.className = "Node";
  //... more such code...
  
  //add div to the container
  container.appendChild(nodeDiv);
  </code></pre>
  
  <p>This code works perfectly fine.
  But now I am using an ExtJs Panel wherein I want to display the same content.
  How do I do it?</p>
  
  <p>I tried doing:</p>
  
  <pre><code>xtype: 'panel',
  autoScroll: true,
  border: 10,
  bodyStyle:{"background-color":"white"}, 
  height: Ext.getBody().getViewSize().height *0.80,
  id: 'treeContainer'
  
  Ext.getCmp('treeContainer').update(nodeDiv); //this didnt work
  Ext.getCmp('treeContainer').addChildEls(nodeDiv); //no success
  </code></pre>
  
  <p>I get this output on firing the below command in debugger: </p>
  
  <pre><code>Ext.getElementById('treeContainer') 
  
  &lt;div class=​"x-panel x-panel-default" style=​"height:​553.6px;​" id=​"treeContainer"&gt;​
  [object HTMLDivElement]
  ​&lt;/div&gt;​
  </code></pre>
  
  <p>Any help!?</p>