Mongoose query: remove "_id" attribute, keep virtual attribute "id" in results

Question

I am running an Express.js app, and I have the following setup:

models.js

var schemaOptions = {
    toJSON: {
      virtuals: true
    },
    toObject: {
        virtuals: true
    }
};

var modelSchema = new mongoose.Schema({
    name     : { type: String, required: true }

}, schemaOptions);

modelSchema.virtual('id').get(function() { return this._id; });

controllers.js

exports.getModel = function(req, res) {
    Model.find().select('name').exec(function(err,model) {
        if (err) {
            return res.status(500).json({errors:err, message: 'Internal server error'});
        }
        return res.status(200).json({model: model});
    });
};

The result of the above query would be something like:

{ "_id":"dakjdjkakda", "name":"MontyPython", "id":"dakjdjkakda" } 

because of the Virtual attribute I defined in the modelSchema.

If I change the query select statement to:

Model.find().select('-_id name').exec(function(err,model) {}

The result would be:

{"name":"MontyPython", "id":null }

I believe this happens because the Virtual attribute points to the _id attribute.

My question is, how can remove the _id attribute in the query, but keep the id alias I created?

Answer 1

If you are using mongoose,

You can handle in when toJSON, you can decide how it display but you can't mention it in your query.

Model.find().select('name').exec(function(err,model) {}

 new mongoose.Schema(yourSchema, {
    toJSON: { 
       transform: function(doc, ret) {
         ret.id = ret._id;
         delete ret._id;
       }
     }
   );}

Answer 2

You might use global approach. Try this one out:

mongoose.plugin((schema) => {
  schema.options.toJSON = {
    virtuals: true,
    versionKey: false,
    transform(doc, ret) {
      ret.id = ret._id;
      delete ret._id;
    }
  };
});

Answer 3

You cannot do that. MongoDB requires _id attribute to be present as per documentation.

Your option is to use virtual attribute as in your example and perhaps $project to hide the field in the query result.

Otherwise, your mongo driver, such as Mongoose, should be able to hide or rename the desired field or attribute.

Answer 4

You can add virtual field id like this as you got it right in your code:

modelSchema.virtual('id').get(function () {

    return this._id;
});

and then remove the actual _id using toJSON's transform option:

modelSchema.set('toJSON', {
    virtuals: true,
    transform: function(doc, ret) {
        delete ret._id;
    }
});

Setting virtuals: true will make sure that your virtual field, i.e. id will be serialized.