How to find if users exist in Firebase? - reactjs

Question

I am using Firebase Web SDK and know methods to check whether a child in a collection exists or not. However I can't find a concise example checking the existence of a user, without trying to sign him/her in.
export class Email extends Component {
constructor (props) {
super(props)
this.state = { email: '' }
}
checkEmail () {
const { email } = this.state
FirebaseApp.auth()
.createUserWithEmailAndPassword(email, uuid.v4())
.then((User) => Actions.Password({ User }))
.catch((error) => {
// Handle Errors here.
console.log('firebase', {error})
this.setState({error})
// ...
})
// Actions.password()
}
render () {
return (
<View style={{ ...styles.onboarding, backgroundColor: 'purple' }}>
<View style={{ borderBottomWidth: 3, borderColor: 'black', padding: 10 }}>
<TextInput ref='email'
style={styles.input}
keyboardType='email-address'
placeholder='Your email'
value={this.state.email}
onChangeText={(email) => this.setState({email: email.toLowerCase()})} />
</View>
{!this.state.error ? null
: <Text>
{this.state.error.message}
</Text>
}
<TouchableOpacity onPress={() => this.checkEmail()} style={{ ...styles.button, margin: 20, borderColor: 'black' }}>
<Text style={styles.buttonText}>Next</Text>
</TouchableOpacity>
</View>
)
}
}
Do you have any piece of code we could reuse?

Answer 1

For the moment, and because it complies with my app security policy and setup, I created an email collection indexed precisely by ids.
firebase.ref(`emails/${user.email}`).set(true)