How to use virtual on a nested field in mongoose - node.js

Question

I am using mongoose in node.js. I have the following Schema.
const CustomerSchema = new mongoose.Schema({
...
email: {
type: String,
required: true,
lowercase: true,
trim: true
},
addresses: [
{
addressType: {
type: String,
enum: [ 'personal', 'shipping', 'billing' ]
},
street: {
type: String,
required: true,
trim: true
},
streetNumber: {
type: String,
trim: true
},
floor: {
type: String,
trim: true
},
apartament: {
type: String,
trim: true
},
cp: {
type: String,
required: true,
trim: true
},
district: {
type: String,
trim: true
},
city: {
type: mongoose.Schema.ObjectId,
ref: 'City',
required: true
}
}
]
});
I want to use "virtuals" to "add" a new field in every object in the array addresses?
How I can do this using virtuals? Is it possible?
I can achieve the same result using, but I would like to use virtuals.
const customerDB = await Customer.findById(idCustomer).lean()
customerDB.addresses = customerDB.addresses.map((address) => ({
...address,
addressDesc: mapTypeAddressDescription(address.addressType)
}));
Many Thanks!

Answer 1

As the name suggests virtuals are not added to the MongoDB documents. They are used for computed properties on documents.
Suppose you have a User model. Every user has an email, but you also want the email's domain. For example, the domain portion of 'test#gmail.com' is 'gmail.com'.
Below is one way to implement the domain property using a virtual. You define virtuals on a schema using the Schema#virtual() function.
const userSchema = mongoose.Schema({
email: String
});
// Create a virtual property `domain` that's computed from `email`.
userSchema.virtual('domain').get(function() {
return this.email.slice(this.email.indexOf('#') + 1);
});
const User = mongoose.model('User', userSchema);
let doc = await User.create({ email: 'test#gmail.com' });
// `domain` is now a property on User documents.
doc.domain; // 'gmail.com'
You should check the documentation for more details.
You can do something like this:
CustomerSchema.path('addresses').schema.virtual('fullAddr').get(function() {
return 'foo'
})
Also, it is useful to check this answer on stackoverflow if the above one doesn't work.