With Mongoose 4.0, you can use Query Hooks in order to autopopulate whatever you want.

Below example is from introduction document by Valeri Karpov.

Definition of Schemas:

var personSchema = new mongoose.Schema({

  name: String

});



var bandSchema = new mongoose.Schema({

  name: String,

  lead: { type: mongoose.Schema.Types.ObjectId, ref: 'person' }

});



var Person = mongoose.model('person', personSchema, 'people');

var Band = mongoose.model('band', bandSchema, 'bands');



var axl = new Person({ name: 'Axl Rose' });

var gnr = new Band({ name: Guns N' Roses, lead: axl._id });

Query Hook to autopopulate:

var autoPopulateLead = function(next) {

  this.populate('lead');

  next();

};



bandSchema.

  pre('findOne', autoPopulateLead).

  pre('find', autoPopulateLead);



var Band = mongoose.model('band', bandSchema, 'bands');