Reference to an object inside an array in another collection - node.js

Question

Following is the WorkingDay model
const workingDaySchema = new mongoose.Schema({
date: { type: String, unique: true, required: true },
availableSlots: [
{
startTime: Date,
endTime: Date,
size: Number,
enrolledUsers: [{ type: Schema.Types.ObjectId, ref: 'Response' }]
}
]
})
module.exports = mongoose.model('WorkingDay', workingDaySchema);
And the following is the Response model:
const responseSchema = new Schema(
{
id: { type: String },
name: { type: String, required: true },
age: { type: String },
gender: { type: String },
height: { type: String },
weight: { type: String },
food: { type: String },
phone: { type: String },
email: { type: String },
category: { type: Array },
answers: { type: Object },
assignedSlot: { type: Schema.Types.ObjectId, ref: availableSlots, default: null }
},
{
timestamps: true,
}
);
module.exports = mongoose.model("Response", responseSchema);
Every object inside the availableSlots array has it own unique _id.
How to create a reference to an object inside availableSlots from the assignedSlot field of response? Also how to populate the same?
I tried referencing the availableSlots objects using
assignedSlot: { type: Schema.Types.ObjectId, ref: availableSlots, default: null }
and
assignedSlot: { type: Schema.Types.ObjectId, ref: "WorkingDay.availableSlots", default: null }
but it did not work.

Answer 1

const { ObjectId } = mongoose.Schema.Types;
assignedSlot: [{ type: ObjectId ,ref:"WorkingDay"}]

Answer 2

Given your schema structure, you should reference the WorkingDay collection:
assignedSlot: { type: Schema.Types.ObjectId, ref: 'WorkingDay', default: null }
Then, you can populate the reference with:
const response = await Response.findOne({}).populate('assignedSlot').exec();
if (response && response.assignedSlot) {
console.log(response.assignedSlot.availableSlots);
}