Check If Firebase User Exist Without Throwing Error - node.js

Question

I have a website that offers a simple messaging service. Individuals can pay for the service, or a business can pay for a monthly subscription and then add their clients/users for free. When the business adds a client/user email, that triggers the function below. I'm using firebase functions and createUser to create the user on my server(less). However, sometimes a business tries to register a user and that user already exist. In this case, I want to send the user a reminder email.
The code I have works fine, but it feels funky having a chain within my catch/error. Is there another way to detect if an email is already registered with a Firebase account that won't throw an error?
exports.newUserRegisteredByBusiness = functions.database.ref('users/{uid}/users/invited/{shortEmail}').onWrite( (data, context) => {
//don't run function if data is null
if (!data.after.val()){
console.log('SKIP: newUserRegisteredByBusiness null so skipping')
return null
} else {
let businessUID = context.params.uid
let email = data.after.val()
let shortEmail = context.params.shortEmail
let password // = something I randomly generate
return admin.auth().createUser({ email: email, password: password}).then( (user)=> {
//write new user data
let updates = {}
let userData // = stuff I need for service to run
updates['users/' + user.uid ] = userData;
return admin.database().ref().update(updates)
}).then( () =>{
//email new user about their new account
return emailFunctions.newUserRegisteredByBusiness(email, password)
}).catch( (error) =>{
//if user already exist we will get error here.
if (error.code === 'auth/email-already-exists'){
//email and remind user about account
return emailFunctions.remindUsersAccountWasCreated(email).then( ()=> {
//Once email sends, delete the rtbd invite value that triggered this whole function
//THIS IS WHERE MY CODE FEELS FUNKY! Is it ok to have this chain?
return admin.database().ref('users/' + businessUID + '/users/invited/' + shortEmail).set(null)
})
} else {
//delete the rtbd value that triggered this whole function
return admin.database().ref('users/' + businessUID + '/users/invited/' + shortEmail).set(null)
}
});
}
})

Answer 1

To find if a user account was already created for a given email address, you call admin.auth().getUserByEmail.
admin.auth().getUserByEmail(email).then(user => {
// User already exists
}).catch(err => {
if (err.code === 'auth/user-not-found') {
// User doesn't exist yet, create it...
}
})
While you're still using a catch() it feels like a much less failed operation.

Answer 2

To avoid further implementation in the catch block you can wrap this Firebase function into this code:
async function checkUserInFirebase(email) {
return new Promise((resolve) => {
admin.auth().getUserByEmail(email)
.then((user) => {
resolve({ isError: false, doesExist: true, user });
})
.catch((err) => {
resolve({ isError: true, err });
});
});
}
...
const rFirebase = await checkUserInFirebase('abc#gmail.com');