A simpler way to update Mongodb documents

mongoose_update_document_the_old_way.js

app.put('/user/:userId', (req, res) => {
  User.findById(req.params.userId, (queryFailedError, user) => {
    if (queryFailedError) {
      res
        .status(500)
        .json({
          errors: [queryFailedError]
        });
    }

    if (!user) {
      res
        .status(404)
        .json({
          errors: ['Record not found']
        });
    }

    // Copy all new properties from req.body.data to our user object
    // Any property on user whose value differs from req.body.data will be updated
    Object.assign(user, req.body.data);

    user.save((saveError) => {
      if (saveError) {
        res
          .status(500)
          .json({
            errors: [saveError]
          });
      }

      res
        .status(204)
        .json({
          success: true
        });
    })
  });
});