User session management in Firebase - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to sign in a user with email and password.

Firebase

firebase.auth().signInWithEmailAndPassword(email, [1])

Drag options to blanks, or click blank then click option'

Atoken

Busername

Cpassword

DsessionId

Attempts:

3 left

💡 Hint

Common Mistakes

Using username instead of password

Using token instead of password

The signInWithEmailAndPassword method requires the user's email and password to authenticate the session.

2fill in blank

medium

Complete the code to check if a user is currently signed in.

Firebase

const user = firebase.auth().[1];

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AcurrentUser

BactiveUser

CsignedInUser

DuserSession

Attempts:

3 left

💡 Hint

Common Mistakes

Using activeUser which does not exist

Using userSession which is not a Firebase property

The currentUser property returns the currently signed-in user or null if no user is signed in.

3fill in blank

hard

Fix the error in the code to sign out the current user.

Firebase

firebase.auth().[1]();

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AsignOut

BsignIn

Clogout

DendSession

Attempts:

3 left

💡 Hint

Common Mistakes

Using signIn instead of signOut

Using logout or endSession which are not Firebase methods

The correct method to sign out a user in Firebase is signOut().

4fill in blank

hard

Fill both blanks to listen for changes in the user's authentication state.

Firebase

firebase.auth().[1]((user) => {
  if (user) {
    console.log('User is signed in:', [2]);
  } else {
    console.log('No user signed in');
  }
});

Drag options to blanks, or click blank then click option'

AonAuthStateChanged

BcurrentUser

Cuser

DauthListener

Attempts:

3 left

💡 Hint

Common Mistakes

Using currentUser instead of onAuthStateChanged

Logging currentUser instead of the callback parameter

The onAuthStateChanged method listens for changes in authentication state. The callback receives the user object when signed in.

5fill in blank

hard

Fill all three blanks to refresh the user's ID token.

Firebase

firebase.auth().currentUser.[1]().then(([2]) => {
  console.log('New token:', [3]);
});

Drag options to blanks, or click blank then click option'

AgetIdToken

Btoken

DrefreshToken

Attempts:

3 left

💡 Hint

Common Mistakes

Using refreshToken method which does not exist

Using different variable names inconsistently

The getIdToken() method refreshes the user's ID token. The token is received in the callback parameter and logged.

Practice

1. What is the main purpose of user session management in Firebase?

easy

A. To keep track of who is logged in and maintain their login state safely

B. To store user data permanently in the database

C. To manage server resources automatically

D. To create user interface themes dynamically

Solution

1. Step 1: Understand user session management

   User session management is about tracking user login status and keeping users logged in securely.

2. Step 2: Identify the correct purpose in Firebase context

   Firebase Auth provides methods to manage user sessions, ensuring users stay logged in safely.

3. Final Answer:

   To keep track of who is logged in and maintain their login state safely -> Option A

4. Quick Check:

   User session management = track and maintain login state [OK]

Hint: Remember: session management = tracking login state [OK]

Common Mistakes:

• Confusing session management with data storage
• Thinking it manages server resources
• Mixing UI features with session handling

2. Which Firebase Auth method is used to sign out a user?

easy

A. firebase.auth().signOut()

B. firebase.auth().endSession()

C. firebase.auth().logOut()

D. firebase.auth().signIn()

Solution

1. Step 1: Recall Firebase Auth sign-out method

   The correct method to sign out a user in Firebase Auth is signOut().

2. Step 2: Verify method names

   Other options like signIn(), logOut(), and endSession() are incorrect or do not exist in Firebase Auth.

3. Final Answer:

   firebase.auth().signOut() -> Option A

4. Quick Check:

   Sign out method = signOut() [OK]

Hint: Sign out uses signOut(), not logOut or endSession [OK]

Common Mistakes:

• Using signIn() instead of signOut()
• Assuming logOut() or endSession() exist
• Confusing signOut() with session ending

3. What will be the output of this code snippet?

firebase.auth().onAuthStateChanged(user => {
  if (user) {
    console.log('User is signed in');
  } else {
    console.log('No user signed in');
  }
});

medium

A. Always logs 'User is signed in'

B. Logs 'User is signed in' if a user is logged in, else 'No user signed in'

C. Throws an error because of syntax

D. Logs nothing because the callback is never called

Solution

1. Step 1: Understand onAuthStateChanged behavior

   This method listens for changes in user authentication state and calls the callback with the user object or null.

2. Step 2: Analyze the callback logic

   If user exists (logged in), it logs 'User is signed in'; otherwise, it logs 'No user signed in'.

3. Final Answer:

   Logs 'User is signed in' if a user is logged in, else 'No user signed in' -> Option B

4. Quick Check:

   onAuthStateChanged logs based on user presence [OK]

Hint: onAuthStateChanged callback runs on login state changes [OK]

Common Mistakes:

• Thinking it always logs 'User is signed in'
• Expecting syntax errors in correct code
• Assuming callback never runs

4. Identify the error in this Firebase session persistence code:

firebase.auth().setPersistence('LOCAL')
  .then(() => {
    return firebase.auth().signInWithEmailAndPassword(email, password);
  })
  .catch(error => {
    console.error(error);
  });

medium

A. 'LOCAL' is not a valid persistence type

B. setPersistence must be called after signInWithEmailAndPassword

C. setPersistence should use firebase.auth.Auth.Persistence.LOCAL constant

D. Missing await keyword before setPersistence

Solution

1. Step 1: Check setPersistence argument

   Firebase expects persistence constants like firebase.auth.Auth.Persistence.LOCAL, not string 'LOCAL'.

2. Step 2: Confirm correct usage

   Using the constant ensures valid persistence setting; strings cause errors.

3. Final Answer:

   setPersistence should use firebase.auth.Auth.Persistence.LOCAL constant -> Option C

4. Quick Check:

   Use persistence constants, not strings [OK]

Hint: Use firebase.auth.Auth.Persistence constants, not strings [OK]

Common Mistakes:

• Passing string instead of constant for persistence
• Calling setPersistence after sign-in
• Forgetting to handle promises

5. You want users to stay signed in only during the browser session (not after closing). Which persistence setting should you use in Firebase Auth?

hard

A. firebase.auth.Auth.Persistence.LOCAL

B. firebase.auth.Auth.Persistence.NONE

C. firebase.auth.Auth.Persistence.PERMANENT

D. firebase.auth.Auth.Persistence.SESSION

Solution

1. Step 1: Understand persistence options

   LOCAL keeps users signed in across browser restarts, SESSION keeps them signed in only during the current tab session, NONE signs out immediately on page reload.

2. Step 2: Match requirement to persistence

   To keep users signed in only during the browser session, SESSION persistence is correct.

3. Final Answer:

   firebase.auth.Auth.Persistence.SESSION -> Option D

4. Quick Check:

   Session persistence = sign-in lasts only during browser session [OK]

Hint: SESSION persistence limits login to current browser session [OK]

Common Mistakes:

• Choosing LOCAL which persists beyond browser close
• Selecting NONE which signs out immediately
• Using non-existent PERMANENT option