Similar to what Suite Resources said, but use some pre-existing records for the classes you want to evaluate:
switch(true){
case req.type == 'customer':
var x = nlapiLoadRecord('class',1000);
and either
return x; OR return x.getAllFields() OR return JSON.stringify(x);
case req.type == 'salesorder':
...... etc.
}
I'd personally just return the whole record to get subfields and prototype functions.