How to create and update referenced documents with mongoose? - node.js

Question

I have this setup
var NotesSchema = new mongoose.Schema({
title: String,
category: [{ type: mongoose.ObjectId, ref: "Categories", default: [] }],
},{ timestamps: { createdAt: 'created_at' } });
var CategoriesSchema = new Schema({
name: {type: String, required: true}
})
var Notes = mongoose.model('Notes', NotesSchema);
var Cat = mongoose.model('Categories', CategoriesSchema);
If I want to create a new note and categories I do this
.get('/new', async (req, res) => {
var post1= {
title : "Post: books, thriller, crime and classics",
favorite : true,
categories:[ 'thriller', 'books']
}
try{
var note = post1.categories.map( (cat)=>{
var ca = new Cat({name: cat})
ca.save()
return ca._id
})
post1.category = note
const newNote = new Notes(post1);
const n = await newNote.save()
res.send(n)
} catch(error) {
console.error(error);
};
})
If I were to create a new note that has some new categories I'm stuck.
var post1= {
...
categories:[ 'thriller', 'books', 'classics']
}
'thriller' and 'books' already exist, but 'classics' doesn't.
I tried Cat.find({"name": {$in: post1.categories}}).exec() but I can't seem to look through that data.
All the example tutorials seem to just add one new entry at a time.

Answer 1

Inside your post1.categories.map callback you are creating the Cat documents and call save() on them but you do not await the returned promise. So Note is created before those promises are fulfilled and thus post1.category will be an empty array.
You can fix this by awaiting the save-promises of the categories:
const savePromises = post1.categories.map((cat) => {
const ca = new Cat({name: cat})
return ca.save();
})
const categoryIds = (await Promise.all(savePromises)).map(category => category._id);
post1.category = categoryIds;
// rest of your code