title: Angular JS - Filter object keys by key names
body: <p>I have object persons</p>
  
  <pre><code>persons = {
      name : 'Thomas M',
      username : 'mthomas',
      company : 'XYZ',
      email : 'tom@xyz.com'
      city : 'Philadelphia',
      country : 'USA'
  };
  </code></pre>
  
  <p>is there any to filter that object by key name i.e if i filter by the keyword - name, it should display 
  name
  username</p>
  
  <p>AngularJS filter works on value but on key value.</p>