title: Ember.js how to concat two objects
body: <p>I have an object in Ember (let's call it <code>existing</code>):</p>
  
  <pre><code> var existing = {
       items: [
          ...
       ],
       ...
   }
  </code></pre>
  
  <p>On the callback of hitting a server side request, there is a new response called <code>result</code> which looks the same as <code>existing</code>. I need to take the <code>items</code> in existing, and prepend them to the new <code>result</code>. So I have the following:</p>
  
  <pre><code>  var result = { ... };
    var existing = this.get('content');
    result.items = result.items.concat(existing.items);
    this.set('content', result);
  </code></pre>
  
  <p>The problem is, when rendered in the template, it is just displaying the new items from <code>result</code>, the old items from <code>existing</code> are not being displayed even though are in <code>items</code>. Any ideas why?</p>
  
  <p>Thanks.</p>