title: Add a new property to Mongoose Document after fetch
body: <p>I have a problem with understanding the variable manipulation in JavaScript. 
  Following code:</p>
  
  <pre><code>UserScore.find(filter, function (err, userScores) {
    var contests = [];
    userScores.forEach(function(userScore)
    {
      contests.push(userScore.ContestId);
    });
    Contest.find({ '_id': { $in : contests } }, function(err, contestItems)
    {
      var result = [];
  
      contestItems.forEach(function(con)
      {
        userScores.forEach(function(element) {
          if(element.ContestId == con._id)
          {
            con.UserTeamName = element.TeamName;
            con.UserPersonalScore = element.Score;
            console.log(con);
            console.log(con.UserPersonalScore);
            result.push(con);
            return;
          }
        });
      });
      res.status(200).json(result);
    });
  });
  </code></pre>
  
  <p>prints "con" without the two added properties, and prints "con.UserPersonalScore" with the appropriate value. When pushed to result, con does not have additional properties. What am I missing?</p>
  
  <p>I guess I am somehow creating local variables instead of properties, but why isn't it being pushed to the result array? </p>