Firebase Admin SDK (Node.js) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the Firebase Admin SDK.

Firebase

const admin = require('firebase-admin');

admin.[1]();

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

AlaunchApp

BinitializeApp

CinitFirebase

DstartApp

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that does not exist like startApp or launchApp.

Forgetting to call the method as a function.

The initializeApp() method starts the Firebase Admin SDK so you can use its services.

2fill in blank

medium

Complete the code to get a Firestore database instance.

Firebase

const db = admin.[1]();

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

Adatabase

BgetDatabase

CgetFirestore

Dfirestore

Attempts:

3 left

💡 Hint

Common Mistakes

Using getFirestore() which is not a method on admin directly.

Using database() which is for Realtime Database, not Firestore.

The firestore() method returns the Firestore database instance from the Admin SDK.

3fill in blank

hard

Fix the error in the code to send a message using Firebase Cloud Messaging.

Firebase

const message = { token: userToken, notification: { title: 'Hello', body: 'World' } };

admin.messaging().[1](message)
  .then(response => console.log('Sent:', response))
  .catch(error => console.error('Error:', error));

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

Asend

Bpublish

CsendMessage

Ddispatch

Attempts:

3 left

💡 Hint

Common Mistakes

Using sendMessage which does not exist in the Admin SDK.

Using publish or dispatch which are not Firebase methods.

The correct method to send a message with Firebase Cloud Messaging is send().

4fill in blank

hard

Fill in the blank to create a new user with email and password using Firebase Admin SDK.

Firebase

admin.auth().[1]({ email: userEmail, password: userPassword })
  .then(userRecord => console.log('User created:', userRecord.uid))
  .catch(error => console.error('Error:', error));

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

AregisterUser

BaddUser

CcreateUser

DnewUser

Attempts:

3 left

💡 Hint

Common Mistakes

Using addUser or registerUser which are not valid Admin SDK methods.

Using newUser which does not exist.

The method to create a new user is createUser().

5fill in blank

hard

Fill in the two blanks to update a user's display name and photo URL.

Firebase

admin.auth().updateUser(userId, { displayName: [1], photoURL: [2] })
  .then(userRecord => console.log('Updated user:', userRecord.uid))
  .catch(error => console.error('Error:', error));

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

A'New Name'

B'https://example.com/photo.jpg'

CuserId

D'Anonymous'

Attempts:

3 left

💡 Hint

Common Mistakes

Using userId as a value for displayName or photoURL.

Not using quotes around string values.

To update user profile fields, provide string values for displayName and photoURL.

Practice

1. What is the primary purpose of the Firebase Admin SDK in Node.js?

easy

A. To build user interfaces for Firebase apps

B. To securely manage Firebase services from a server environment

C. To run Firebase apps directly in the browser

D. To replace Firebase client SDK on mobile devices

Solution

1. Step 1: Understand Firebase Admin SDK role

   The Admin SDK is designed for server-side use to manage Firebase services securely.

2. Step 2: Differentiate from client SDKs

   Client SDKs run on user devices for app interaction, while Admin SDK runs on servers for management tasks.

3. Final Answer:

   To securely manage Firebase services from a server environment -> Option B

4. Quick Check:

   Admin SDK = server management [OK]

Hint: Admin SDK is for backend server tasks, not frontend apps [OK]

Common Mistakes:

• Confusing Admin SDK with client SDK
• Thinking Admin SDK runs in browsers
• Assuming Admin SDK builds UI

2. Which of the following is the correct way to initialize the Firebase Admin SDK in Node.js using a service account JSON file named serviceAccountKey.json?

easy

A. const admin = require('firebase-admin');
admin.initializeApp({credential: admin.credential.cert(require('./serviceAccountKey.json'))});

B. const admin = require('firebase-admin');
admin.initializeApp({serviceAccount: 'serviceAccountKey.json'});

C. const admin = require('firebase-admin');
admin.initializeApp({credential: admin.credential.applicationDefault()});

D. const admin = require('firebase-admin');
admin.initializeApp({credential: admin.credential.cert(serviceAccountKey.json)});

Solution

1. Step 1: Load service account JSON correctly

   The service account JSON must be imported using require to pass the object, not a string path.

2. Step 2: Use admin.credential.cert with the JSON object

   Pass the imported JSON object to admin.credential.cert for proper initialization.

3. Final Answer:

   const admin = require('firebase-admin'); admin.initializeApp({credential: admin.credential.cert(require('./serviceAccountKey.json'))}); -> Option A

4. Quick Check:

   Use require() to load JSON for cert [OK]

Hint: Use require() to load JSON, not a string path [OK]

Common Mistakes:

• Passing file path string instead of JSON object
• Using applicationDefault() when service account is needed
• Incorrect property name like 'serviceAccount'

3. Given the following Node.js code using Firebase Admin SDK, what will be the output if the user with UID 'user123' exists?

const admin = require('firebase-admin');
admin.initializeApp();

admin.auth().getUser('user123')
  .then(userRecord => console.log(userRecord.uid))
  .catch(error => console.log('Error:', error.message));

medium

A. user123

B. Error: User not found

C. undefined

D. null

Solution

1. Step 1: Understand getUser() behavior

   getUser() returns a Promise resolving to a user record if the user exists.

2. Step 2: Check the then() callback output

   The code logs userRecord.uid, which will be 'user123' if the user exists.

3. Final Answer:

   user123 -> Option A

4. Quick Check:

   getUser() returns user data, logs UID [OK]

Hint: getUser() returns user info; log uid to see user ID [OK]

Common Mistakes:

• Assuming getUser() returns error if user exists
• Expecting undefined or null instead of UID
• Not handling Promise correctly

4. Identify the error in the following Firebase Admin SDK Node.js code snippet:

const admin = require('firebase-admin');
admin.initializeApp({
  credential: admin.credential.cert(serviceAccountKey.json)
});

admin.auth().createUser({
  email: '[e-mail]',
  password: 'secret123'
}).then(userRecord => console.log(userRecord.uid));

medium

A. initializeApp() cannot accept credential property

B. Password must be at least 10 characters

C. createUser() requires a displayName field

D. The service account JSON file path should be required, not passed as a string

Solution

1. Step 1: Check initialization of credential

   admin.credential.cert() expects a JSON object, not a string path. The file must be loaded with require().

2. Step 2: Validate other parameters

   Password length and displayName are optional or valid; initializeApp() accepts credential property.

3. Final Answer:

   The service account JSON file path should be required, not passed as a string -> Option D

4. Quick Check:

   Use require() to load JSON for cert [OK]

Hint: Load JSON with require(), not string path [OK]

Common Mistakes:

• Passing string path instead of JSON object
• Assuming password length error
• Thinking displayName is mandatory

5. You want to send a push notification to a device using Firebase Admin SDK in Node.js. Which sequence of steps correctly applies to achieve this?

hard

A. Use Firebase client SDK to send notification directly from server without Admin SDK

B. Initialize Admin SDK with credentials, call admin.auth().sendNotification(token, message), then handle response

C. Initialize Admin SDK with credentials, build a message object with token and notification, then call admin.messaging().send(message)

D. Initialize Admin SDK without credentials, build message, then call admin.database().send(message)

Solution

1. Step 1: Initialize Admin SDK properly

   Admin SDK must be initialized with credentials to access Firebase services securely.

2. Step 2: Create message object and send

   Build a message with device token and notification details, then use admin.messaging().send() to send it.

3. Final Answer:

   Initialize Admin SDK with credentials, build a message object with token and notification, then call admin.messaging().send(message) -> Option C

4. Quick Check:

   Use admin.messaging().send() with message object [OK]

Hint: Use admin.messaging().send() with message object and token [OK]

Common Mistakes:

• Using auth() instead of messaging() for notifications
• Trying to send without initializing SDK
• Using database() to send notifications