Functions custom claims example

index.js

exports.userCreationListener = functions.auth.user().onCreate(user => {
    const admins = {
        "first@admin.com": true
    };
    const email = user.email;
    if (!admins[email]) {
        return false;
    }
    const uid = user.uid;
    return admin.auth().setCustomUserClaims(uid, {superAdmin: true}).then(
        ()=>admin.database().ref(`users/${uid}`).set(true)).catch(error=>{
        console.log("SUPER_ADMIN_UPDATE_ERROR", error);
        return false;
    });
});