Chaining Firebase Firestore documents/collections - firebase

Question

So, I have a Firestore database group like so.
companies > acme-industries > items > []
OR
collection > document > collection > document
Would it be better to just store all items inside a base collection and then add a string value to each item that defines what company it goes too? Then just query the items collection for all items linked to that company?
I am trying to retrieve the items and run them through a forEach in my firebase function. I have tried two different approaches and watched multiple videos and still am not getting results.
First Attempt Code Block
This resulted in a 500 Server Error with no explanation returned.
const itemQuerySnapshot = db.collection('companies').doc(data.userData.company).collection('items').get();
const items: any = [];
itemQuerySnapshot.forEach((doc:any) => {
console.log('doc', doc.data());
items.push({
id: doc.id,
data: doc.data()
});
});
response.json(items);
Second Attempt Code Block
This resulted in the No Such Documents! being returned
const itemRef = db.collection('companies').doc(data.userData.company).collection('items');
itemRef.get().then((doc:any) => {
if(!doc.exists) {
response.send('No such documents!');
} else {
response.send('Document Data: '+ doc.data());
}
}).catch((err:any) => {
response.status(500).send(err);
});
I am expecting something like an array of all the items to be returned from this call. I'm completely new to Firebase Firestore, what am I missing here?
UPDATE
I replaced my code with a third attempt code block and I got success with the console.log(doc.data()). However, the items object still returns empty. Is this because it's returning before the for each is done? If so, how would you prevent that to ensure every item that should be returned is?
const items: any = [];
const userRef = db.collection("companies").doc(data.userData.company);
const itemsRef = userRef.collection("items");
itemsRef
.get()
.then((snapshot: any) => {
snapshot.forEach((doc: any) => {
console.log(doc.data());
items.push({
id: doc.id,
data: doc.data()
});
});
})
.catch((err: any) => {
response.status(500).send(err);
});
response.json(items);
How would you add one more document into the mix? Say you want to get a single item. How would you do that? The following always results in Item does not exist being returned from my function.
const companyRef = db.collection('companies').doc(data.userData.company);
const itemRef = companyRef.collection('items');
const item = itemRef.where('number', '==', itemSku).get();
I must be doing something incredibly wrong here because all the videos are telling me it's incredibly easy to fetch data from Firestore. But I have yet to see that.

Answer 1

get returns a Promise , the callback of then function will be called once the data ready from firestore .
the line response.json(items); will be called before the items array collected correctly.
you need to move this line inside the then callback
checkout this :
.then((snapshot: any) => {
snapshot.forEach((doc: any) => {
console.log(doc.data());
items.push({
id: doc.id,
data: doc.data()
});
});
response.json(items); //items ARRAY IS READY , YOU CAN SEND YOUR RESPONSE HERE
})