Firebase app not accessing functions (e.g. firebase.auth()) - firebase

Question

I'm having this problem that I've spent hours looking into but can't seem to figure out. I'm trying to use Firebase with Node.js, but am unable to access the different Firebase functions (e.g. firebase.auth() and firebase.firestore()). However, when I initialize via the admin SDK, those end up working. Below is my simple code as well as the error:
const functions = require('firebase-functions');
const firebase = require('firebase');
const app = express();
firebase.initializeApp(functions.config().firebase);
const auth = firebase.auth();
const db = firebase.firestore();
And the resulting error: TypeError: firebase.auth is not a function
Note I also had a few lines initializing express and handlebars but doubt those would have had any impact.
I've also tried including "require("firebase/auth")" but that hasn't worked. Below is also my package.json, specifically the modules I have installed:
"dependencies": {
"consolidate": "^0.15.1",
"express": "^4.16.3",
"firebase": "^5.0.4",
"firebase-admin": "~5.12.1",
"firebase-functions": "^1.0.4",
"firebase-tools": "^3.18.6",
"firebaseauth": "^1.0.0",
"handlebars": "^4.0.11"
},
Any help please? I'm a bit of a novice web developer so any advice would be much appreciated. Thank you!

Answer 1

Cloud Functions triggers have a format like this:
exports.myFunctionName = functions.firestore
.document('users/marie').onWrite((change, context) => {
// ... Your code here
});
You cannot access the client-side SDKs from inside a Cloud Function. Instead, if there are features you want to access inside a Cloud Function, you can use the Admin SDKs.
var admin = require('firebase-admin');
var app = admin.initializeApp();

Answer 2

Short answer: Use the admin SDK, that's what it's for - Cloud Functions to interact with the rest of your backend.
Longer answer:
To help you along, here is an example of a working index.js file for a Firebase Cloud Function that accesses both the database (not firestore) and the auth portion of Firebase... with some comments to provide context. It's an API endpoint that accepts a user's token, verifies that the user is an 'admin' in my system, and then creates a new user account before responding with the new UID.
const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
exports.createUser = functions.https.onRequest( (req, res) => {
// Look at the accessToken provided in the request, and have Firebase verify whether it's valid or not
admin.auth().verifyIdToken(req.body.accessToken).then(decodedIdToken => {
// Token was valid, pull the UID out of the token for the user making this request
let requestorUid = decodedIdToken.uid;
// Make a query to the database to see what that user's role is
admin.database().ref(`userBasicInfo/${requestorUid}/role`).once('value').then( dataSnapshot => {
if (dataSnapshot.val() === 'admin') {
// If their role is "admin" then let's create a user!
let userEmail = `${req.body.newuserid}#company.org`;
admin.auth().createUser({
email: userEmail,
password: req.body.password
}).then(userRecord => {
// See the UserRecord reference doc for the contents of userRecord.
res.send({uid: userRecord.uid});
}).catch( error => {
console.log("Error creating user:");
console.log(error)
res.send(false);
});
} else {
console.log('Checked the database for the UID provided in the access token, role was not "admin".');
res.send(false);
}
}).catch( err => {
console.log('Error finding user in database:');
console.log(err);
res.send(false);
})
}).catch( error => {
console.error('Error while verifying Firebase ID token:');
console.log(error);
res.send(false);
});
});
And the package.json would be:
{
"name": "functions",
"description": "Cloud Functions for Firebase",
"scripts": {
"serve": "firebase serve --only functions",
"shell": "firebase experimental:functions:shell",
"start": "npm run shell",
"deploy": "firebase deploy --only functions",
"logs": "firebase functions:log"
},
"dependencies": {
"firebase-admin": "^5.11.0",
"firebase-functions": "^1.0.2"
},
"private": true
}