title: Convert object to array while removing non-number field names
body: <p>Is it possible to convert an object to an array if it has this structure, while all fields are ignored which have an non-number field?</p>
  
  <pre><code>var obj = {
      0: 'some',
      1: 'thing',
      2: 'to convert',
      ignore: 'this'
  }
  </code></pre>
  
  <p>result should be:</p>
  
  <pre><code>result = ['some', 'thing', 'to convert'];
  </code></pre>
  
  <p>with the correct order of the elements.</p>