title: How focus a textbox after using extjs Ext.MessageBox.alert
body: <p>I want to validate my extjs form. When the text field is empty, there should display an alert box and after that our cursor have to focus on the text box. I tried with the coding below. Alert is working fine. but cursor is not focusing. Can you please help me anybody to focus?</p>
  
  <pre><code>if(Ext.get('first').dom.value=='')
  {
      Ext.MessageBox.alert('Status', 'Enter your First Name!');
      document.getElementById("first").focus();
  }
  </code></pre>