Linking multiple providers in Firebase - Mini Project: Build & Apply

Linking Multiple Providers in Firebase Authentication

📖 Scenario: You are building a mobile app that allows users to sign in using different providers like Google and Facebook. To keep user accounts unified, you want to link these providers to a single Firebase user account.

🎯 Goal: Build a Firebase Authentication setup that links a Google provider and a Facebook provider to the same user account.

📋 What You'll Learn

Create a Firebase user object with a Google provider credential

Create a Facebook provider credential variable

Link the Facebook provider credential to the existing Firebase user

Complete the linking process with proper error handling

💡 Why This Matters

🌍 Real World

Apps often let users sign in with multiple providers to make login easier and keep accounts unified.

💼 Career

Understanding how to link multiple authentication providers is key for developers working with Firebase Authentication in real projects.

1

Create a Firebase user with Google provider credential

Create a variable called user that simulates a Firebase user object with a method linkWithCredential. Also create a variable called googleCredential with the exact string value 'google-credential-token'.

Firebase

// Your code here

Need a hint?

Think of user as an object with a method to link credentials. The googleCredential is just a string token here.

2

Create a Facebook provider credential variable

Create a variable called facebookCredential and assign it the exact string value 'facebook-credential-token'.

Firebase

const user = {
  linkWithCredential: async function(credential) {
    return `Linked with ${credential}`;
  }
};
const googleCredential = 'google-credential-token';

// Your code here

Need a hint?

This is similar to the Google credential but for Facebook.

3

Link the Facebook provider credential to the existing Firebase user

Use await user.linkWithCredential(facebookCredential) inside an async function called linkProviders to link the Facebook credential to the user.

Firebase

const user = {
  linkWithCredential: async function(credential) {
    return `Linked with ${credential}`;
  }
};
const googleCredential = 'google-credential-token';
const facebookCredential = 'facebook-credential-token';

// Your code here

Need a hint?

Wrap the linking call inside an async function so you can use await.

4

Complete the linking process with error handling

Add a try and catch block inside the linkProviders function to catch errors from user.linkWithCredential(facebookCredential). In the catch, assign the error to a variable called error.

Firebase

const user = {
  linkWithCredential: async function(credential) {
    return `Linked with ${credential}`;
  }
};
const googleCredential = 'google-credential-token';
const facebookCredential = 'facebook-credential-token';

async function linkProviders() {
  // Add try-catch for error handling
  // Your code here
}

Need a hint?

Use try and catch to safely handle errors during linking.