No automatic _id generated - node.js

Question

So I have this code for adding a new item to the database, like so:
let parking = new Parking({
name: req.body.name,
country: mongoose.Types.ObjectId(req.body.country),
reservationsEmail: req.body.reservationsEmail,
location: mongoose.Types.ObjectId(req.body.location),
commissionPercentage: req.body.commission,
isConcept: true,
});
parking.save()
.then(parking => {
res.send(parking);
}).catch(err => {
res.send(err);
});
This gives me an error that _id is required before saving:
{ MongooseError: document must have an _id before saving
at new MongooseError (/Users/robin/www_node/parkos/node_modules/mongoose/lib/error/mongooseError.js:14:11)
at Timeout._onTimeout (/Users/robin/www_node/parkos/node_modules/mongoose/lib/model.js:259:18)
at ontimeout (timers.js:466:11)
at tryOnTimeout (timers.js:304:5)
at Timer.listOnTimeout (timers.js:267:5)
message: 'document must have an _id before saving',
name: 'MongooseError' }
Why isn't the _id automatically added like it supposed to?
This is the model I use:
const mongoose = require('mongoose');
const ObjectId = mongoose.Schema.ObjectId;
const isEmail = require('validator/lib/isEmail');
const slugify = require('../../lib/utils.js').slugify;
let parkingSchema = new mongoose.Schema({
name: {
type: String,
required: true,
},
slug: {
type: String,
required: true,
default() {
return slugify(this.name);
}
},
country: {
type: ObjectId,
ref: 'Country',
required: true,
},
reservationsEmail: {
type: String,
required: true,
validate: [
isEmail,
'Please enter a valid emailaddress'
],
},
discountPercentage: {
type: String,
required() {
return !this.isConcept;
},
default: 0,
},
location: {
type: ObjectId,
required: true,
ref: 'Location'
},
commissionPercentage: {
type: Number,
required: true,
},
isConcept: {
type: Boolean,
required: true,
default: false,
},
active: {
type: Boolean,
default: true,
},
}, {
timestamps: true,
});
const Parking = mongoose.model('Parking', parkingSchema);
module.exports = Parking;
Values for both country and location in request:
console.log('Location', parking.location, typeof parking.location); // Location 5caa0993ab95691762dc1a33 object
console.log('Country', parking.country, typeof parking.country); // Country 5caa04e6b6969a708080f8dd object
So when I post it via Postman:
{
"name": "Test Parking",
"reservationsEmail": "example#gmail.com",
"country": "5caa04e6b6969a708080f8dd",
"location": "5caa0993ab95691762dc1a33",
"commission": "20"
}
It works like expected... via the Fetch API though...
let formData = new URLSearchParams([...new FormData(form).entries()]);
fetch('/parkings/create-concept', {
method: "POST",
body: formData,
credentials: "include",
}).then(response => {
console.log(response);
}).catch(err => {
console.log(err);
});

Answer 1

In your model.js have you this line ?
module.exports = mongoose.model('Parking', parkingSchema);
=======================
Country and location must be instance of objectId, try to set them with
mongoose.Types.ObjectId(req.body.myfield);