title: Add a value in combobox without a store
body: <p>I am using REST services to communicate with the server and that function returns a HashMap. I need to use this HashMap to populate the combobox. I have made an ajax request for retrieving that HashMap (in a javascript var). Now that I have this HashMap I need to add the 'keys' as options in the combobox. </p>
  
  <p>Is it possible with the help of some insert function without creating a store since my HashMap is itself like a store. How do I accomplish this?</p>
  
  <p>I wanted to do something like this : </p>
  
  <pre><code>for (var field in json) {
      combo.add(field) // Is there any function or a way by which I can do this
  }
  </code></pre>