Modular SDK (v9+) tree-shaking in Firebase - Mini Project: Build & Apply

Modular SDK (v9+) Tree-Shaking with Firebase

📖 Scenario: You are building a simple web app that uses Firebase for authentication and Firestore database. To keep your app fast and small, you want to use Firebase's Modular SDK (v9+) which supports tree-shaking. This means you only import the parts of Firebase you actually use.

🎯 Goal: Create a Firebase app setup using the Modular SDK (v9+) with tree-shaking. You will initialize Firebase, configure authentication, and set up Firestore with minimal imports to keep the bundle size small.

📋 What You'll Learn

Use Modular SDK imports from 'firebase/app', 'firebase/auth', and 'firebase/firestore'

Initialize Firebase app with given config object

Create an auth instance using getAuth

Create a db instance using getFirestore

Avoid importing entire Firebase namespaces to enable tree-shaking

💡 Why This Matters

🌍 Real World

Using Firebase Modular SDK with tree-shaking is essential for building fast, efficient web apps that only load the code they need.

💼 Career

Many companies use Firebase for backend services. Knowing how to use the Modular SDK properly is a valuable skill for frontend and full-stack developers to optimize app performance.

1

Create Firebase configuration object

Create a constant called firebaseConfig with the exact keys and values: apiKey: 'AIzaSyA-1234567890abcdef', authDomain: 'myapp.firebaseapp.com', projectId: 'myapp', storageBucket: 'myapp.appspot.com', messagingSenderId: '1234567890', appId: '1:1234567890:web:abcdef123456'.

Firebase

# Your code here

Hint

Use const firebaseConfig = { ... } with the exact keys and values.

2

Import and initialize Firebase app

Import initializeApp from 'firebase/app'. Then create a constant called app by calling initializeApp(firebaseConfig).

Firebase

const firebaseConfig = {
  apiKey: 'AIzaSyA-1234567890abcdef',
  authDomain: 'myapp.firebaseapp.com',
  projectId: 'myapp',
  storageBucket: 'myapp.appspot.com',
  messagingSenderId: '1234567890',
  appId: '1:1234567890:web:abcdef123456'
};

// Import initializeApp and initialize Firebase app
// Your code here

Hint

Use import { initializeApp } from 'firebase/app' and then const app = initializeApp(firebaseConfig).

3

Set up Firebase Authentication and Firestore

Import getAuth from 'firebase/auth' and getFirestore from 'firebase/firestore'. Create constants auth and db by calling getAuth(app) and getFirestore(app) respectively.

Firebase

import { initializeApp } from 'firebase/app';

const firebaseConfig = {
  apiKey: 'AIzaSyA-1234567890abcdef',
  authDomain: 'myapp.firebaseapp.com',
  projectId: 'myapp',
  storageBucket: 'myapp.appspot.com',
  messagingSenderId: '1234567890',
  appId: '1:1234567890:web:abcdef123456'
};

const app = initializeApp(firebaseConfig);

// Import getAuth and getFirestore and create auth and db
// Your code here

Hint

Import getAuth and getFirestore and create auth and db using the app instance.

4

Export Firebase instances for use in app

Add export statements to export the constants app, auth, and db so they can be used in other parts of your app.

Firebase

import { initializeApp } from 'firebase/app';
import { getAuth } from 'firebase/auth';
import { getFirestore } from 'firebase/firestore';

const firebaseConfig = {
  apiKey: 'AIzaSyA-1234567890abcdef',
  authDomain: 'myapp.firebaseapp.com',
  projectId: 'myapp',
  storageBucket: 'myapp.appspot.com',
  messagingSenderId: '1234567890',
  appId: '1:1234567890:web:abcdef123456'
};

const app = initializeApp(firebaseConfig);

const auth = getAuth(app);
const db = getFirestore(app);

// Export app, auth, and db
// Your code here

Hint

Use export { app, auth, db } to make these available outside this module.

Practice

1. What is the main benefit of using Firebase Modular SDK (v9+) with tree-shaking?

easy

A. It reduces app size by including only needed Firebase features.

B. It automatically backs up your Firebase database.

C. It increases the number of Firebase services loaded by default.

D. It disables Firebase authentication for faster login.

Solution

1. Step 1: Understand tree-shaking purpose

   Tree-shaking removes unused code to reduce app size and improve performance.

2. Step 2: Apply to Firebase Modular SDK

   Using modular imports in Firebase v9+ allows only needed services to be included, enabling tree-shaking.

3. Final Answer:

   It reduces app size by including only needed Firebase features. -> Option A

4. Quick Check:

   Tree-shaking = smaller app size [OK]

Hint: Remember: modular imports keep only what you use [OK]

Common Mistakes:

• Thinking tree-shaking adds features automatically
• Confusing tree-shaking with backup or security
• Assuming all Firebase services load by default

2. Which import statement correctly uses Firebase Modular SDK (v9+) for Firestore to enable tree-shaking?

easy

A. import { Firestore } from 'firebase/app';

B. import { getFirestore } from 'firebase/firestore';

C. import firebase from 'firebase';

D. import * as firestore from 'firebase/firestore';

Solution

1. Step 1: Identify modular import syntax

   Firebase v9+ uses named imports from specific service packages like 'firebase/firestore'.

2. Step 2: Check each option

   import { getFirestore } from 'firebase/firestore'; correctly imports getFirestore from 'firebase/firestore' for modular usage. Others use old or incorrect syntax.

3. Final Answer:

   import { getFirestore } from 'firebase/firestore'; -> Option B

4. Quick Check:

   Modular import = named import from service path [OK]

Hint: Use named imports from 'firebase/service' for modular SDK [OK]

Common Mistakes:

• Using default import from 'firebase' package
• Importing from 'firebase/app' instead of service path
• Using wildcard imports that prevent tree-shaking

3. Given the code below, what will be the output in the console?

import { initializeApp } from 'firebase/app';
import { getAuth } from 'firebase/auth';

const app = initializeApp({ apiKey: 'abc', authDomain: 'xyz' });
const auth = getAuth(app);
console.log(typeof auth.currentUser);

medium

A. 'null'

B. 'undefined'

C. 'function'

D. 'object'

Solution

1. Step 1: Understand getAuth and currentUser

   getAuth returns an Auth instance; currentUser is a property that is either null or a user object.

2. Step 2: Check typeof currentUser before login

   Before login, currentUser is null, and typeof null is 'object' in JavaScript.

3. Final Answer:

   'object' -> Option D

4. Quick Check:

   typeof null = 'object' in JS [OK]

Hint: Remember: typeof null returns 'object' in JavaScript [OK]

Common Mistakes:

• Assuming currentUser is undefined before login
• Confusing typeof null with 'null' string
• Thinking currentUser is a function

4. Identify the error in this Firebase Modular SDK (v9+) import code:

import { initializeApp } from 'firebase/app';
import { getFirestore } from 'firebase/firestore';

const app = initializeApp(config);
const db = getFirestore();

medium

A. getFirestore() requires the app instance as an argument.

B. initializeApp should be imported from 'firebase/firestore'.

C. config object is missing from the code.

D. getFirestore must be called before initializeApp.

Solution

1. Step 1: Check usage of initializeApp

   initializeApp requires a config object to initialize Firebase app.

2. Step 2: Verify presence of config object

   The code uses 'config' but does not define or import it, causing a ReferenceError.

3. Final Answer:

   config object is missing from the code. -> Option C

4. Quick Check:

   Missing config causes initialization error [OK]

Hint: Always define config before initializeApp call [OK]

Common Mistakes:

• Forgetting to pass app to getFirestore (optional but recommended)
• Importing initializeApp from wrong package
• Calling getFirestore before app initialization

5. You want to optimize your Firebase app bundle size by importing only Authentication and Firestore services using Modular SDK (v9+). Which code snippet correctly achieves this with tree-shaking?

hard

A. import { initializeApp } from 'firebase/app';
import { getAuth } from 'firebase/auth';
import { getFirestore } from 'firebase/firestore';

const app = initializeApp(config);
const auth = getAuth(app);
const db = getFirestore(app);

B. import firebase from 'firebase';

const app = firebase.initializeApp(config);
const auth = firebase.auth();
const db = firebase.firestore();

C. import { initializeApp, getAuth, getFirestore } from 'firebase/app';

const app = initializeApp(config);
const auth = getAuth(app);
const db = getFirestore(app);

D. import { initializeApp } from 'firebase/app';
import { auth, firestore } from 'firebase';

const app = initializeApp(config);
const authInstance = auth(app);
const dbInstance = firestore(app);

Solution

1. Step 1: Use modular imports from correct packages

   Authentication and Firestore must be imported from 'firebase/auth' and 'firebase/firestore' respectively for tree-shaking.

2. Step 2: Initialize app and pass it to service getters

   Initialize app with config, then pass app instance to getAuth and getFirestore functions.

3. Step 3: Check each option

   import { initializeApp } from 'firebase/app'; import { getAuth } from 'firebase/auth'; import { getFirestore } from 'firebase/firestore'; const app = initializeApp(config); const auth = getAuth(app); const db = getFirestore(app); correctly imports and initializes services modularly. Others use old syntax or wrong imports preventing tree-shaking.

4. Final Answer:

   Option A code snippet -> Option A

5. Quick Check:

   Modular imports + app passed = optimized bundle [OK]

Hint: Import each service from its own package and pass app [OK]

Common Mistakes:

• Using default firebase import disables tree-shaking
• Importing multiple services from 'firebase/app' only
• Not passing app instance to service getters