Cannot add property to mongoose document with findOneAndUpdate - node.js

Question

My express app tries to record the login time of the user using Mongoose's findOneAndUpdate.
router.post('/login', passport.authenticate('local', {
failureFlash: true,
failureRedirect: '/'
}), async(req, res, next) => {
// if we're at this point in the code, the user has already logged in successfully.
console.log("successful login")
// save login time to database
const result = await User.findOneAndUpdate({ username: req.body.username }, { loginTime: Date.now() }, { new: true });
console.log(result);
return res.redirect('/battle');
})
The user document does not start out with a login time property. I'm expecting this code to insert that property for me.
The actual result is, the console shows the user document being printed out, but without any added login time property. How can I fix this so a login time property is inserted into the document? Is the only way to do it by defining a login time property in the original mongoose schema? And if so, doesn't that nullify the supposed advantage of NoSQL vs SQL in that it's supposed to allow new unexpected property types into your collections and documents?

Answer 1

I've found the answer for anyone who might come across the same problem. It is not at all possible to add a property to a Mongoose collection if it is not already defined in the Schema. So to fix it I added the property in the Schema.

Answer 2

In fact, you can add a new property that isn't defined in the schema, without modifying the schema. You need to set the flag strict to false to enable this mode. See document here.
The code below demonstrates what I said, feel free to runs it:
const mongoose = require('mongoose');
// connect to database
mongoose.connect('mongodb://localhost/test', { useNewUrlParser: true, useUnifiedTopology: true, useFindAndModify: false });
// define the schema
const kittySchema = new mongoose.Schema({
name: String
// this flag indicate that the shema we defined is not fixed,
// document in database can have some fields that are not defined in the schema
// which is very likely
}, { strict: false });
// compile schema to model
const Kitten = mongoose.model('Kitten', kittySchema);
test();
async function test() {
// empty the database
await Kitten.deleteMany({});
// test data
const dataObject = { name: "Kitty 1" };
const firstKitty = new Kitten(dataObject);
// save in database
await firstKitty.save();
// find the kitty from database
const firstKittyDocument = await Kitten.findOne({ name: "Kitty 1" });
console.log("Mongoose document", firstKittyDocument);
// modify the kitty, add new property doesn't exist in the schema
const firstKittyDocumentModified = await Kitten.findOneAndUpdate(
{ _id: firstKittyDocument._id },
{ $set: { age: 1 } },
{ new: true }
);
console.log("Mongoose document updated", firstKittyDocumentModified);
// note : when we log the attribute that isn't in the schema, it is undefined :)
console.log("Age ", firstKittyDocumentModified.age); // undefined
console.log("Name", firstKittyDocumentModified.name); // defined
// for that, use .toObject() method to convert Mongoose document to javascript object
const firstKittyPOJO = firstKittyDocumentModified.toObject();
console.log("Age ", firstKittyPOJO.age); // defined
console.log("Name", firstKittyPOJO.name); // defined
}
The output:
Mongoose document { _id: 60d1fd0ac3b22b4e3c69d4f2, name: 'Kitty 1', __v: 0 }
Mongoose document updated { _id: 60d1fd0ac3b22b4e3c69d4f2, name: 'Kitty 1', __v: 0, age: 1 }
Age undefined
Name Kitty 1
Age 1
Name Kitty 1