title: how to jsonify an array containing objects with custom jsonification
body: <p>So I have a CustomObject and an array containing a number of them.</p>
  
  <p>Right now, when I say res.json(myArray), I get a standard jsonification of my CustomObject, i.e. field1:value, field2:value, ....</p>
  
  <p>What I can not figure out is how to make a custom jsonification of my CustomObject, such as I only want to return a subset of the parameters.</p>
  
  <p>What functions do I have to customize? In CustomObject only?</p>