Why does mongoose return object IDs' in the form of an object with an ID as a Buffer instead of string?

Question

I have a static method in my UnitSchema that finds a unit by a token. It gets passed a token as a parameter and tries to find the unit with a normal findOne method on the Unit model:

UnitSchema.statics.findByToken = async function (token) {
  const Unit = this
  let unit = await Unit.findOne({ 'Tokens.token': token }).populate('Organisation')
  return unit
}

I have had this method for a long time and it has always returned the correct object. Now, which seems like all of a sudden for no reason, it returns a "complete" mongoose object with all of the extra information and functions, and all the object ID's are now in an object format instead of a string format, such as:

ObjectID {
  _bsontype: 'ObjectID',
  id: <Buffer 5c 85 43 16 f1 ad 70 d8 f8 97 48 78> 
}

instead of:

_id: '5d49595246853f14fc5168e9'

Because of this I can no longer populate fields with the normal: .populate('field') and this breaks my code.

I have searched around like crazy but can not find an explanation for this, and therefore I do not know how to fix it. Help is kindly appreciated!

Answer 1

I know this is a late answer. But I faced this issue recently and did some search on why the response is given in an Array of Buffer instead of an id. But I couldn't find any resource regarding it.

But, to convert the Buffer into an id. Just use String or toString().