Sometimes, we want to modify the data returned by a Mongoose query in Node.js.

In this article, we’ll look at how to modify the data returned by a Mongoose query in Node.js.

How to modify the data returned by a Mongoose query in Node.js?

To modify the data returned by a Mongoose query in Node.js, we can call lean to make Mongoose return a plain object version of the query result that we can modify.

For instance, we write

Survey.findById(req.params.id).lean().exec((err, data) => {
  data.surveyQuestions.forEach((sq) => {
    Question.findById(sq.question, (err, q) => {
      sq.question = q;
    });
  });
});

to call lean after call findById to make the data in the exec callback a plain JavaScript object version of the query result.

We then loop through each item in data.surveyQuestions and set sq.question to q on each entry in the Question.findById callback.

Conclusion

To modify the data returned by a Mongoose query in Node.js, we can call lean to make Mongoose return a plain object version of the query result that we can modify.