Facebook sign-in in Firebase - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Facebook sign-in in Firebase?

Facebook sign-in in Firebase allows users to log into your app using their Facebook account, making login easy and secure without creating a new password.

beginner

Which Firebase service handles Facebook sign-in?

Firebase Authentication handles Facebook sign-in by connecting your app with Facebook's login system and managing user sessions.

intermediate

What do you need to set up before enabling Facebook sign-in in Firebase?

You need a Facebook Developer account, create a Facebook app, get the App ID and App Secret, and configure these in Firebase console under Authentication providers.

intermediate

How does Firebase use the Facebook access token during sign-in?

Firebase uses the Facebook access token to verify the user's identity with Facebook and then creates a Firebase user session based on that verification.

advanced

What is a common error when Facebook sign-in fails in Firebase?

A common error is misconfigured OAuth redirect URIs or incorrect Facebook App ID/Secret, which prevents Firebase from verifying the Facebook login.

What is the first step to enable Facebook sign-in in Firebase?

A Create a Facebook app and get App ID and Secret

B Write code to handle Facebook login

C Deploy Firebase project

D Create a Google Cloud project

You must first create a Facebook app to get the App ID and Secret before configuring Firebase.

Which Firebase feature manages Facebook sign-in?

A Firebase Authentication

B Firebase Firestore

C Firebase Hosting

D Firebase Functions

Firebase Authentication manages user sign-in including Facebook sign-in.

What does Firebase use to verify a Facebook user during sign-in?

A User email

B Firebase API key

C Facebook access token

D OAuth redirect URI

Firebase uses the Facebook access token to verify the user's identity.

Where do you configure Facebook App ID and Secret for Firebase sign-in?

A Firebase Realtime Database

B Firebase Storage

C Firebase Cloud Messaging

D Firebase Authentication providers settings

Facebook App ID and Secret are configured in Firebase Authentication providers.

What is a common cause of Facebook sign-in failure in Firebase?

A Incorrect Firebase project name

B Misconfigured OAuth redirect URI

C Missing Firebase API key

D No internet connection

Misconfigured OAuth redirect URI often causes Facebook sign-in failures.

Explain the steps to set up Facebook sign-in in Firebase from scratch.

Think about what you need on Facebook and Firebase sides before coding.

Describe how Firebase uses the Facebook access token during the sign-in process.

Focus on token flow and verification.

Practice

1. What is the main purpose of using Facebook sign-in with Firebase?

easy

A. To create Facebook accounts automatically

B. To store user data in Facebook servers

C. To replace Firebase authentication completely

D. To let users log in using their Facebook account easily

Solution

1. Step 1: Understand Facebook sign-in purpose

   Facebook sign-in allows users to authenticate using their existing Facebook account, simplifying login.

2. Step 2: Compare options

   Only To let users log in using their Facebook account easily correctly describes this purpose; others describe unrelated or incorrect uses.

3. Final Answer:

   To let users log in using their Facebook account easily -> Option D

4. Quick Check:

   Facebook sign-in = Easy login with Facebook [OK]

Hint: Facebook sign-in means easy login with Facebook account [OK]

Common Mistakes:

• Thinking Facebook sign-in stores data on Facebook
• Confusing Facebook sign-in with full Firebase replacement
• Assuming Facebook creates accounts automatically

2. Which Firebase method is used to start Facebook sign-in with a popup window?

easy

A. signInWithPopup

B. signInWithRedirect

C. signInWithEmailAndPassword

D. createUserWithEmailAndPassword

Solution

1. Step 1: Identify Firebase methods for sign-in

   Firebase offers signInWithPopup and signInWithRedirect for OAuth providers like Facebook.

2. Step 2: Choose method for popup

   signInWithPopup opens a popup window for login, matching the question requirement.

3. Final Answer:

   signInWithPopup -> Option A

4. Quick Check:

   Popup login method = signInWithPopup [OK]

Hint: Popup login uses signInWithPopup method [OK]

Common Mistakes:

• Confusing redirect and popup methods
• Using email/password methods for Facebook sign-in
• Mixing createUser with sign-in methods

3. What will the following code do?

const provider = new firebase.auth.FacebookAuthProvider();
firebase.auth().signInWithPopup(provider)
  .then(result => console.log(result.user.displayName))
  .catch(error => console.error(error));

medium

A. Log the user's Facebook display name after successful sign-in

B. Throw a syntax error because of missing semicolons

C. Log an error because Facebook sign-in is not supported

D. Create a new Facebook account automatically

Solution

1. Step 1: Analyze the code flow

   The code creates a Facebook provider, calls signInWithPopup, then logs the user's display name on success.

2. Step 2: Check for errors or unsupported features

   Code syntax is correct; Facebook sign-in is supported; no account creation happens automatically.

3. Final Answer:

   Log the user's Facebook display name after successful sign-in -> Option A

4. Quick Check:

   signInWithPopup success logs displayName [OK]

Hint: signInWithPopup logs user info on success [OK]

Common Mistakes:

• Thinking missing semicolons cause errors
• Assuming Facebook sign-in is unsupported
• Believing code creates Facebook accounts

4. You get an error when calling signInWithPopup for Facebook sign-in. What is a common cause?

medium

A. Using signInWithEmailAndPassword instead

B. Facebook sign-in is not enabled in Firebase console

C. Not importing Firebase SDK

D. Calling signInWithPopup without a provider

Solution

1. Step 1: Identify common setup errors

   Facebook sign-in requires enabling it in Firebase console under Authentication providers.

2. Step 2: Evaluate other options

   Using wrong methods or missing imports cause different errors; calling without provider causes immediate failure.

3. Final Answer:

   Facebook sign-in is not enabled in Firebase console -> Option B

4. Quick Check:

   Enable Facebook sign-in in Firebase console [OK]

Hint: Enable Facebook sign-in in Firebase console first [OK]

Common Mistakes:

• Forgetting to enable Facebook provider
• Mixing signInWithEmailAndPassword with Facebook sign-in
• Ignoring SDK import errors
• Calling signInWithPopup without provider argument

5. You want to add Facebook sign-in to your app and ensure users' Facebook profile pictures are saved in Firebase user profiles. Which steps are needed?

hard

A. Use signInWithEmailAndPassword and fetch Facebook pictures separately

B. Only enable Facebook sign-in; Firebase saves profile pictures automatically

C. Enable Facebook sign-in in Firebase, use signInWithPopup, then update user profile with photoURL from Facebook data

D. Create Facebook accounts manually and link to Firebase users

Solution

1. Step 1: Enable Facebook sign-in

   Enable Facebook provider in Firebase console under Authentication > Sign-in method.

2. Step 2: Authenticate and update profile

   Implement signInWithPopup (or Redirect) with FacebookAuthProvider; then update the Firebase user profile with the photoURL obtained from Facebook data to ensure profile pictures are saved.

3. Final Answer:

   Enable Facebook sign-in in Firebase, use signInWithPopup, then update user profile with photoURL from Facebook data -> Option C

4. Quick Check:

   Enable Facebook provider + signInWithPopup + update profile photoURL [OK]

Hint: Firebase requires manual update of photoURL after Facebook sign-in [OK]

Common Mistakes:

• Believing manual photoURL update is not required
• Using signInWithEmailAndPassword for Facebook login
• Manually creating Facebook accounts instead of linking