Change _id Type

You can easily change the type of the _id field by doing:

class SomeChangedID {
  @prop()
  public _id: string; // change the type of _id to string
}

note

When the type is manually set (having an @prop, even for ObjectId), then the value need to be always defined before saving, or using the default option

To disable the _id field altogether (useful in arrays of subdocuments), add option @prop({ _id: false }) or on the subdocument class @modelOptions({ schemaOptions: { _id: false } }) (This option has no effect when the class / schema is the root schema).

@modelOptions({ schemaOptions: { _id: false } }) // either with the schema option
class WithNoId {
  @prop()
  public someValue: string;
}

class SomeChangedID {
  @prop({ type: WithNoId, _id: false }) // or with the prop-option
  public someField: WithNoId[];
}

With the Base Class

There is also a Base interface typegoose provides, which includes _id and id, which can be used as follows:

interface Something extends Base<string> {} // have the interface to add the types of "Base" to the class
class Something { // have your class, OR
  @prop()
  public _id: string;
}
class Something extends TimeStamps { // have your class extend some other class
  @prop()
  public _id: string;
}

note

The _id property needs to also be included in the actual class, because the default interface Base doesn't change anything at runtime (Base does not use @prop).

Restriction

This method (extending Base) can only be used with types that are in RefType (all of mongoose.Schema.Types should work except Array, Mixed, Boolean).