title: How do I add temporary properties on a mongoose object just for response, which is not stored in database
body: <p>I would like to fill a couple of extra temporary properties with additional data and send back to the response</p>
  
  <pre><code>'use strict';
  
  var mongoose = require('mongoose');
  var express = require('express');
  var app = express();
  
  var TournamentSchema = new mongoose.Schema({
      createdAt: { type: Date, default: Date.now },
      deadlineAt: { type: Date }
  });
  
  var Tournament = mongoose.model('Tournament', TournamentSchema);
  
  app.get('/', function(req, res) {
      var tournament = new Tournament();
  
      // Adding properties like this 'on-the-fly' doesnt seem to work
      // How can I do this ?
      tournament['friends'] = ['Friend1, Friend2'];
      tournament.state = 'NOOB';
      tournament.score = 5;
      console.log(tournament);
      res.send(tournament);
  });
  
  var server = app.listen(3000, function() {
      console.log('Listening on port %d', server.address().port);
  });
  </code></pre>
  
  <p>But the properties wont get added on the Tournament object and therefor not in the response.</p>