RegistrationScreen.js

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import { firebase } from '../../firebase/config'

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export default function RegistrationScreen({navigation}) {
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    const onRegisterPress = () => {
        if (password !== confirmPassword) {
            alert("Passwords don't match.")
            return
        }
        firebase
            .auth()
            .createUserWithEmailAndPassword(email, password)
            .then((response) => {
                const uid = response.user.uid
                const data = {
                    id: uid,
                    email,
                    fullName,
                };
                const usersRef = firebase.firestore().collection('users')
                usersRef
                    .doc(uid)
                    .set(data)
                    .then(() => {
                        navigation.navigate('Home', {user: data})
                    })
                    .catch((error) => {
                        alert(error)
                    });
            })
            .catch((error) => {
                alert(error)
        });
    }
    
    ...
}