request to Firebase for once read data-CodePudding

I have this construction for reading data from Firebase (it's for 8 version Firebase).

const info = (await firebase.database().ref(`/users/${uid}/info`).once('value')).val

But I use version 9 Firebase. I saw example in Firebase manual, but can't adapt for my example.

These examples from manual: (version 9)

import { getDatabase, ref, onValue } from "firebase/database";
import { getAuth } from "firebase/auth";

const db = getDatabase();
const auth = getAuth();

const userId = auth.currentUser.uid;
return onValue(ref(db, '/users/'   userId), (snapshot) => {
  const username = (snapshot.val() && snapshot.val().username) || 'Anonymous';
  // ...
}, {
  onlyOnce: true
});

(Version 8):

var userId = firebase.auth().currentUser.uid;
return firebase.database().ref('/users/'   userId).once('value').then((snapshot) => {
  var username = (snapshot.val() && snapshot.val().username) || 'Anonymous';
  // ...
});

CodePudding user response：

onValue() sets a listener for data changes at a particular location.

In your case, you want to read the data once since you use the once() method in V8.

So the corresponding V9 syntax is:

import { getDatabase, ref, child, get } from "firebase/database";

const dbRef = ref(getDatabase());
get(child(dbRef, `/users/${uid}/info`)).then((snapshot) => {
  if (snapshot.exists()) {
    var username = (snapshot.val() && snapshot.val().username) || 'Anonymous';
    // ...
  } else {
    console.log("No data available");
  }
}).catch((error) => {
  console.error(error);
});

More details in the doc.