inefficient-save.js

function completedChallenge(req, res, next) {
  const { user, body } = req;
  // mutates user object
  const { alreadyCompleted } = updateUserProgress(user, body);
  // sends entire user object to database
  return saveUser(req.user)
    .subscribe(
      () => {},
      next,
      function() {
        return res.json({
          points: user.progressTimestamps.length,
          alreadyCompleted
        });
      }
    );
}