Is there a way to pass user Id to schema?

Question

I have a user schema and an exam schema, i wanted to pass the id of the user to the schema of the exam

const ExamSchema = new mongoose.Schema({
-----> _id: [{
    class: { type: String, required: true },
    module: { type: Number,required:true },
    date: {type: Date, required: true }
  }]

Where it says _id - i wanted it to be the id of the user! Should i do it like this or add the exams schema on the user schema? Like this?

const UserSchema = new mongoose.Schema({
  username: { type: String, require: true },
  email: { type: String, required: true, unique: true },
  password: { type: String, required: true },
  active: { type: Boolean, default: true },
  exam: [{
    class: { type: String, required: true },
    module: { type: Number,required:true },
    date: {type: Date, required: true }
  }]
});

Answer 1

Check Mongoose "Populate"

https://mongoosejs.com/docs/populate.html

A part from the docs,

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const personSchema = Schema({
  _id: Schema.Types.ObjectId,
  name: String,
  age: Number,
  stories: [{ type: Schema.Types.ObjectId, ref: 'Story' }]
});

const storySchema = Schema({
  author: { type: Schema.Types.ObjectId, ref: 'Person' },
  title: String,
  fans: [{ type: Schema.Types.ObjectId, ref: 'Person' }]
});

const Story = mongoose.model('Story', storySchema);
const Person = mongoose.model('Person', personSchema);

So far we've created two Models. Our Person model has its stories field set to an array of ObjectIds. The ref option is what tells Mongoose which model to use during population, in our case the Story model. All _ids we store here must be document _ids from the Story model.

In your case just make a user_id in Exam Schema and refer to id of User Schema

const ExamSchema = new mongoose.Schema({
    user_id: {type: Schema.Types.ObjectId, ref: 'User' },
    class: { type: String, required: true },
    module: { type: Number,required:true },
    date: {type: Date, required: true }
  })