Creating an array of mongodb objects?

Question

Node.js

const chatSchema = {
  id: {
    type: Number,
    required: true,
  },
   chatName: {
     type: String
     required: true,
  },
    chatCreated {
      type: Number,
      required: true,
  },
}

and I need to make after chatCreated chatUser which will contain each user from the conversation.