CODEWITHSUNDEEP
node.jsmongodbmongoose
esgy
esgy

Reputation: 392

Does MongooseJS return a new fresh result object on save()?

By default MongoDB on collection.save() returns a WriteResult object as stated in the documentation:

The save() returns a WriteResult object that contains the status of the insert or update operation.

But with Mongoose (and I guess the underlying mongodb driver in node) you can add a second parameter that is populated with the entire object that you just inserted and with the new _id:

var user = new User(req.body);

user.save(function (err, userResult) {
    if (err) {
        log.error(err);
    }
    log.debug('User data: ', userResult);
});

So my question: Does userResult contain retrieved data from Mongo and it's a fresh object OR is the object passed already passed into the save() method and from the database call is merged with only some partial data like the generated _id and/or created date?

Upvotes: 2

Views: 329

Answers (2)

Katherine R
Katherine R

Reputation: 1158

To answer your question, the object returned is a new object -- not the original one (so user != userResult)

Mongoose supports a few options -- new: true and lean: false settings may be of interest to you to modify how data is returned in different operations (if you want it to be a new option or do not care).

You can verify this 'new object' is the case by using the following:

var user = new User(req.body);

user.save(function (err, userResult) {
    if (err) {
        log.error(err);
    }

    user.name = 'TEST';
    console.log(`${userResult.name} will be undefined but ${user.name} will not be`);
    log.debug('User data: ', userResult);
});

Upvotes: 0

Andrew Lavers
Andrew Lavers

Reputation: 8141

If you take a look at Model.prototype.save():

https://github.com/Automattic/mongoose/blob/8cb0e35/lib/model.js#L254

It looks like you get back the same model instance (self) in your userResult.

Upvotes: 1

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