How to fetch the _id of the subdocument from array

[illay_senner]

I have a collection of list that contain invitee information as an array of objects like below:

const InviteeListSchema = new Schema([
  {
    //add this part later on to link a list to the host
    // it should look up for host ID etc. Make sure it is INT/NUMBER
    // host_id: {},
    ownerId: { type: Schema.Types.ObjectId, ref: "Customer_Host", required: true },
    invitees: [
      {
        _id: { type: Schema.Types.ObjectId, required: true, auto: true },
        firstname: { type: String, required: true },
        lastname: { type: String, required: false },
        email: { type: String, required: true },
        //emailConfirm: { type: String, required: true },
        mobile: { type: String, required: false },
        createdAt: { type: Date, required: true, default: Date.now() },
        lastUpdatedAt: { type: Date, required: true, default: Date.now() },
        isDeleted: { type: Boolean, required: true, default: false }
      }
    ],
    createdAt: { type: Date, required: true, default: Date.now() },
    lastUpdatedAt: { type: Date, required: true, default: Date.now() },
    isDeleted: { type: Boolean, required: true, default: false }

  }]);

I want to be able to add/push new objects into the invitees array. However, I am having issues getting the newly created object within invitees array.

I have tried findandupdate, but returns the entire object. tried updateOne, but doesn’t return the new objectID. I am wondering if there is a one step/elegant way to achieve this? Otherwise it requites at least 2 steps, where the second step would be a find() method to fetch the last array item from invitees.

Keen to hear the experts thoughts on this.

Thanks in advance

[John_Sewell]

Are you passing the optional parameter to return the updated document as opposed to the document before the update?

[illay_senner]

This is what I get from each queries:

db.invitee_lists.updateOne({_id:ObjectId("64fa8e44cb08d093f33d0a08")},{$push: {'invitees':{'firstname':'Ilay'}}},{new:true, returnNewDocument: true})

{
  acknowledged: true,
  insertedId: null,
  matchedCount: 1,
  modifiedCount: 1,
  upsertedCount: 0
}

[illay_senner]

and

db.invitee_lists.findOneAndUpdate({_id:ObjectId("64fa8e44cb08d093f33d0a08"),},{$push: {'invitees':{'firstname':'Ilay', "_id":new ObjectId()}}},{new:true, returnNewDocument:true})

_id: ObjectId("64fa8e44cb08d093f33d0a08"),
  ownerId: ObjectId("64f845f0f4e46cb7a0467053"),
  invitees: [
    {
      _id: ObjectId("64fa8e44cb08d093f33d0a09"),
      firstname: 'firstname',
      lastname: 'lastname',
      email: 'myemail@gmail.com',
      mobile: '0400000111',
      createdAt: 2023-09-08T01:40:51.946Z,
      lastUpdatedAt: 2023-09-08T01:40:51.946Z,
      isDeleted: false
    },
    {
      _id: ObjectId("64fa8e44cb08d093f33d0a0a"),
      firstname: 'Micky,
      lastname: 'Lee',
      email: 'myemail@yahoo.com',
      mobile: '+6140000000',
      createdAt: 2023-09-08T01:40:51.946Z,
      lastUpdatedAt: 2023-09-08T01:40:51.946Z,
      isDeleted: false
    },
   {
      firstname: 'Ilay',
      _id: ObjectId("65039d48b6a4eb9cb140d6d9")
    }
  ],
  createdAt: 2023-09-08T01:40:51.946Z,
  lastUpdatedAt: 2023-09-08T01:40:51.946Z,
  isDeleted: false,
  __v: 0
}

type or paste code here

type or paste code here

[illay_senner]

by trial and error, used projection: { ‘invitees’: { $slice: -1 } } … using any other parameter/element in projection breaks it…

thanks for the prompt response, appreciated.