How to do this with Firebase version 9 Web SDK
db.collection('rooms')
.doc(id)
.collection('messages')
.orderBy('timestamp', 'asc')
.onSnapshot((snapshot) =>
setState(snapshot.docs.map(doc =>
doc.data()))
)
The following should do the trick:
import { collection, query, orderBy, onSnapshot } from "firebase/firestore";
const id = ...;
const messagesColRef = collection(db, "rooms", id, "comments");
const messagesQuery = query(messagesColRef, orderBy("timestamp"));
onSnapshot(messagesQuery, (snapshot) => {
setState(snapshot.docs.map(doc =>
doc.data()))
});
Have a look at the Firestore reference.
related to your question indirectly, if you want to procrastinate and upgrade to 9 but leave your code as is, you can use the version 9 compat (Compatibility) link. Just replace your version 8 with version 9 and add "-compat" before ending '.js' .e.g.
<script src="https://www.gstatic.com/firebasejs/9.3.0/firebase-app-compat.js"></script>
this way don't change your code while using latest version of firebase. The disadvantage is that you won't benefit from module nature firebase 9.