Why serverless functions extend Firebase - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize Firebase Functions in your project.

Firebase

const functions = require('[1]');

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

Afirebase-functions

Bfirebase-admin

Cfirebase-auth

Dfirebase-storage

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'firebase-admin' instead of 'firebase-functions' to write functions.

Confusing storage or auth packages with functions.

The firebase-functions package is used to write serverless functions that extend Firebase capabilities.

2fill in blank

medium

Complete the code to create an HTTP triggered serverless function.

Firebase

exports.helloWorld = functions.[1]((req, res) => { res.send('Hello from Firebase!'); });

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

Ahttps.onCall

Bhttps

Cdatabase

Dhttps.onRequest

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'https' without '.onRequest' which is incomplete.

Using 'https.onCall' which is for callable functions from clients.

The https.onRequest method creates an HTTP function that responds to web requests.

3fill in blank

hard

Fix the error in the function trigger to respond to Firestore document creation.

Firebase

exports.newUser = functions.firestore.document('[1]').onCreate((snap, context) => { console.log('New user added'); });

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

Ausers/userId

Busers

Cusers/{userId}

Dusers/*

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'users/userId' which listens to a fixed document, not any document.

Using 'users' which is a collection, not a document path.

The path users/{userId} uses a wildcard to trigger on any new user document creation.

4fill in blank

hard

Fill both blanks to create a function that triggers on Firebase Authentication user creation and logs the user ID.

Firebase

exports.logNewUser = functions.auth.user().[1]((user) => { console.log('User ID:', user.[2]); });

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

AonCreate

Buid

ConDelete

Demail

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'onDelete' instead of 'onCreate' for user creation events.

Accessing 'email' instead of 'uid' when logging user ID.

The onCreate trigger runs when a user is created, and uid accesses the user's unique ID.

5fill in blank

hard

Fill all three blanks to write a Firestore function that updates a user's profile when their document changes.

Firebase

exports.updateUserProfile = functions.firestore.document('[1]').[2]((change, context) => { const newData = change.[3].data(); console.log('Updated data:', newData); });

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

Ausers/{userId}

BonUpdate

Cafter

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'data' instead of 'after' to get new document data.

Using 'onCreate' instead of 'onUpdate' for document changes.

The function triggers on updates to any user document (users/{userId}) using onUpdate. The new document data is accessed with after.data().

Practice

1. What is the main benefit of using serverless functions with Firebase?

easy

A. They only work on mobile devices.

B. You need to set up and maintain your own servers.

C. They replace the Firebase database completely.

D. You can run backend code without managing servers.

Solution

1. Step 1: Understand serverless functions

   Serverless functions let you write backend code that runs automatically without you managing servers.

2. Step 2: Compare options

   Serverless functions do not require server management, do not replace the database, and work on all platforms.

3. Final Answer:

   You can run backend code without managing servers. -> Option D

4. Quick Check:

   Serverless = no server management [OK]

Hint: Serverless means no servers to manage [OK]

Common Mistakes:

• Thinking serverless means no backend code
• Confusing serverless with database replacement
• Believing serverless only works on mobile

2. Which of the following is the correct way to define a Firebase serverless function triggered by a database write?

easy

A. exports.myFunc = functions.database.ref('/path').onWrite((change, context) => { /* code */ });

B. functions.database.onWrite('/path', (change, context) => { /* code */ });

C. exports.myFunc = functions.onWrite('/path', (change, context) => { /* code */ });

D. functions.database.ref('/path').write((change, context) => { /* code */ });

Solution

1. Step 1: Recall Firebase function syntax

   The correct syntax uses exports to define the function and functions.database.ref(path).onWrite() to trigger on database writes.

2. Step 2: Check each option

   exports.myFunc = functions.database.ref('/path').onWrite((change, context) => { /* code */ }); matches the correct syntax. The other options have incorrect method calls or missing exports.

3. Final Answer:

   exports.myFunc = functions.database.ref('/path').onWrite((change, context) => { /* code */ }); -> Option A

4. Quick Check:

   Correct Firebase function syntax = exports.myFunc = functions.database.ref('/path').onWrite((change, context) => { /* code */ }); [OK]

Hint: Look for exports and onWrite with ref path [OK]

Common Mistakes:

• Omitting exports keyword
• Using wrong method names like write instead of onWrite
• Incorrect function chaining order

3. Given this Firebase function code:

exports.greetUser = functions.auth.user().onCreate((user) => {
  return `Hello, ${user.email}!`;
});

What will this function do when a new user signs up?

medium

A. Return a greeting string but does not send it anywhere.

B. Trigger an error because return type is wrong.

C. Send a greeting email automatically.

D. Delete the user account immediately.

Solution

1. Step 1: Analyze function trigger and return

   The function triggers on user creation and returns a greeting string but does not send or log it anywhere.

2. Step 2: Understand side effects

   Returning a string alone does not send emails or cause errors. No deletion code is present.

3. Final Answer:

   Return a greeting string but does not send it anywhere. -> Option A

4. Quick Check:

   Return alone does not send email [OK]

Hint: Return value alone doesn't trigger actions [OK]

Common Mistakes:

• Assuming return sends email automatically
• Thinking function deletes user without code
• Believing return type causes error

4. You wrote this Firebase function:

exports.logChange = functions.database.ref('/items/{id}').onUpdate((change, context) => {
  console.log('Item updated');
});

But it never logs anything when the database updates. What is the likely problem?

medium

A. onUpdate is not a valid trigger method.

B. The database path '/items/{id}' is invalid syntax.

C. The function is missing a return statement or promise.

D. console.log cannot be used in Firebase functions.

Solution

1. Step 1: Check function structure

   Firebase functions should return a promise or value to signal completion. Missing return can cause silent failures.

2. Step 2: Validate other options

   Path syntax is correct, console.log works for debugging, and onUpdate is valid trigger.

3. Final Answer:

   The function is missing a return statement or promise. -> Option C

4. Quick Check:

   Return missing causes no execution [OK]

Hint: Always return or await in Firebase functions [OK]

Common Mistakes:

• Forgetting to return or await async work
• Assuming console.log doesn't work
• Misreading trigger method names

5. You want to extend your Firebase app to send a welcome email only when a new user signs up and their email is verified. Which approach best uses serverless functions to achieve this?

hard

A. Use a database trigger on user data write, ignoring email verification status.

B. Use an auth trigger on user creation, check if emailVerified is true, then send email.

C. Send emails directly from the client app after signup.

D. Use a scheduled function to send emails to all users daily.

Solution

1. Step 1: Identify correct trigger and condition

   Auth triggers on user creation allow checking user properties like emailVerified immediately.

2. Step 2: Evaluate options for sending email

   Use an auth trigger on user creation, check if emailVerified is true, then send email, which checks emailVerified before sending, ensuring only verified users get emails. The other options do not meet the requirement precisely.

3. Final Answer:

   Use an auth trigger on user creation, check if emailVerified is true, then send email. -> Option B

4. Quick Check:

   Auth trigger + emailVerified check = Use an auth trigger on user creation, check if emailVerified is true, then send email. [OK]

Hint: Check emailVerified in auth trigger before emailing [OK]

Common Mistakes:

• Sending emails without verifying email status
• Using database triggers for auth events
• Sending emails from client risking security