react native firebase check if user already exisits in real time database

Question

i need to check if username already exists in real time database then prompt user to select another username. it keep saying not found. I think it because of how my data is nested.

signup.js

const { email, username, password } = this.state;

    await firebase
                .auth()
                .createUserWithEmailAndPassword(email, password)
                .then(async user => {
                    console.log('Data created', user);
                    let rootRef = firebase.database().ref()

                rootRef.child("users")
                        .orderByChild("username")
                        .equalTo(username)
                        .once("value")
                        .then(snapshot => {
                            if (snapshot.exists()) {
                                    let userData = snapshot.val()
                                console.log(userData)
                              Alert.alert('username is taken')
                                return userData;
                            }else {
                                console.log('not found')

                            }
                    })

Answer 1

You are creating a user, then check if that user exists. Check if the user exists before creating the user.

const { email, username, password } = this.state;

let rootRef = firebase.database().ref();

rootRef
  .child('users')
  .orderByChild('username')
  .equalTo(username)
  .once('value')
  .then(snapshot => {
    if (snapshot.exists()) {
      let userData = snapshot.val();
      console.log(userData);
      Alert.alert('username is taken');
      return userData;
    } else {
      console.log('not found');
      firebase
        .auth()
        .createUserWithEmailAndPassword(email, password)
        .then(async user => {
          console.log('Data created', user);
        });
    }
});