How do I get nested reference data in firestore? - firebase

Question

I'm trying to get data by dates and render html in firestore,
But I cannot that.
The order is wrong.
Because, The data is sorted by user.
How do I get data by date?
{
comments: {
comment_1: {
userRef: users/user_1,
body: "body",
createdAt: Timestamp,
},
comment_2: {
userRef: users/user_2,
body: "body",
createdAt: Timestamp,
},
comment_3: {
userRef: users/user_1,
body: "body",
createdAt: Timestamp,
},
},
users: {
user_1 : {
name: "test"
},
user_2 : {
name: "test"
},
}
}
db.collection('comments').orderBy('createdAt').get().then(snapshot=> {
const comment = snapshot.data();
comment.userRef.get().then(userSnapshot => {
const userData = userSnapshot.data();
const comment = document.getElementById('js-comment');
const element = document.createElement('div')
element.innerHTML = `<p>${comment.body}</p>`
comment.appendChild(element);
});
});

Answer 1

You need to sort the data using orderBy the date field as you have in the code, however, you do not have a field createdAt in the data model you have provided.
If your comments data looks like this
comments: {
comment_1: {
userRef: users/user_1,
body: "body",
createdAt: Timestamp
},
comment_2: {
userRef: users/user_2,
body: "body",
createdAt: Timestamp
},
comment_3: {
userRef: users/user_1,
body: "body",
createdAt: Timestamp
},
The timestamp field can be filled in by getting firestore to fill the field using Timestamp.now() when the data is created.
Once the data is read using the orderBy for the comments. You need to specify ASCENDING if you want the data to be increasing order, then the users can be looked up and the data should appear in the correct order.
This is discussed more here https://firebase.google.com/docs/firestore/query-data/order-limit-data