How to hided __v property in mongoose?

In Mongoose, the __v property is a version key that is added by default to MongoDB documents to represent the document's version. If you want to exclude this property from query results, there are multiple approaches to achieve this.

1. Exclude __v Property During Query Execution

When executing queries, you can exclude this field by setting __v: 0 in the projection parameter of the query.

javascript
Model.find({}, { __v: 0 }).then(result => {
    console.log(result);
});

2. Use Schema Options to Globally Hide __v

When defining a Mongoose Schema, you can set versionKey to false, which hides the __v field in all instances of the model.

javascript
const schema = new mongoose.Schema({ name: String }, { versionKey: false });
const Model = mongoose.model('Model', schema);

const doc = new Model({ name: 'Hide __v example' });
console.log(doc); // `__v` will not be part of the document

3. Use Virtual Properties to Filter __v

Virtual properties are a highly flexible feature in Mongoose. You can define a virtual property to retrieve the document object excluding the __v field.

javascript
schema.virtual('documentWithoutVersionKey').get(function() {
    const obj = this.toObject();
    delete obj.__v;
    return obj;
});

After that, you can use this virtual property to retrieve the document object without the __v property.

4. Use toJSON and toObject Transformation Options

In the Schema definition, you can set the transform option for toJSON and toObject to exclude __v.

javascript
schema.set('toJSON', {
    transform: function(doc, ret, options) {
        delete ret.__v;
        return ret;
    }
});

schema.set('toObject', {
    transform: function(doc, ret, options) {
        delete ret.__v;
        return ret;
    }
});

This way, the __v field is automatically excluded whenever you call toJSON() or toObject().

Example

For instance, suppose you have a user model and you don't want to return the __v field in any API response. You can set versionKey: false when defining the user Schema:

javascript
const userSchema = new mongoose.Schema({
    username: String,
    email: String
}, { versionKey: false });

const User = mongoose.model('User', userSchema);

This way, whenever you create an instance of the user model, it will not include the __v field.

Summary

In summary, hiding the __v property can be achieved either by dynamically excluding it during queries or by setting global options in the model definition based on project requirements.