Cloud Functions setup in Firebase - Commands & Configuration

Introduction

Cloud Functions let you run small pieces of code in the cloud when something happens, like a user signing up. This setup helps you write and deploy these functions easily without managing servers.

When you want to send a welcome email automatically after a user signs up.

When you need to process images uploaded to your app without slowing down the user.

When you want to update a database record whenever a file changes.

When you want to run backend code triggered by events without managing servers.

When you want to keep your app logic secure by running it in the cloud.

Config File - package.json

package.json

{
  "name": "functions",
  "scripts": {
    "lint": "eslint .",
    "build": "tsc",
    "serve": "firebase emulators:start --only functions",
    "shell": "firebase functions:shell",
    "start": "npm run shell",
    "deploy": "firebase deploy --only functions",
    "logs": "firebase functions:log"
  },
  "engines": {
    "node": "18"
  },
  "main": "lib/index.js",
  "dependencies": {
    "firebase-admin": "^11.10.1",
    "firebase-functions": "^4.4.0"
  },
  "devDependencies": {
    "eslint": "^8.44.0",
    "eslint-config-google": "^0.14.0",
    "typescript": "^5.1.3"
  },
  "private": true
}

This file defines the Cloud Functions project settings.

• scripts: Commands to build, test, and deploy functions.
• engines: Specifies Node.js version 18, the current supported version.
• dependencies: Required Firebase libraries for functions.
• devDependencies: Tools for code quality and TypeScript support.

Commands

Starts the setup wizard to create a Cloud Functions project in your Firebase app. It creates necessary files and folders.

Terminal

firebase init functions

Expected Output

=== Project Setup ===



You're about to initialize a Firebase Functions project.



? What language would you like to use to write Cloud Functions? (Use arrow keys)

> JavaScript

  TypeScript



? Do you want to use ESLint to catch probable bugs and enforce style? Yes



? Do you want to install dependencies with npm now? Yes



✔  Wrote functions/package.json

✔  Wrote functions/index.js

✔  Wrote .eslintrc.js

✔  Wrote .gitignore



✔  Initialized Cloud Functions project.



Next steps:

  1. Write functions in functions/index.js

  2. Deploy with firebase deploy --only functions

Uploads and activates your Cloud Functions code to Firebase so they start running in the cloud.

Terminal

firebase deploy --only functions

Expected Output

=== Deploying to 'your-project-id' ===



i  deploying functions

Running command: npm --prefix "$RESOURCE_DIR" run lint



> functions@ lint /workspace/functions

> eslint .





✔  functions: Finished running lint.



i  functions: ensuring necessary APIs are enabled...

✔  functions: all necessary APIs are enabled



i  functions: preparing functions directory for uploading...



✔  functions: functions folder uploaded successfully



✔  Deploy complete!



Project Console: https://console.firebase.google.com/project/your-project-id/overview



Function URL (helloWorld): https://us-central1-your-project-id.cloudfunctions.net/helloWorld

→

--only functions - Deploys only the Cloud Functions part, not other Firebase services.

Shows recent logs from your deployed Cloud Functions to help you check if they run correctly or find errors.

Terminal

firebase functions:log

Expected Output

2024-06-01T12:00:00.000Z your-project-id helloWorld: Function execution started

2024-06-01T12:00:01.000Z your-project-id helloWorld: Function execution finished

Key Concept

If you remember nothing else from this pattern, remember: initializing with 'firebase init functions' sets up your project structure and deploying with 'firebase deploy --only functions' makes your code run in the cloud.

Common Mistakes

Not running 'npm install' inside the functions folder after initialization

Your functions won't have the required libraries to run, causing errors during deployment or execution.

Run 'npm install' inside the functions directory or choose to install dependencies during 'firebase init functions' setup.

Deploying without specifying '--only functions' when you only want to update functions

This can unintentionally deploy other Firebase services, which might cause delays or unwanted changes.

Use 'firebase deploy --only functions' to deploy only your Cloud Functions.

Not checking logs with 'firebase functions:log' after deployment

You miss important runtime errors or confirmation that your functions work as expected.

Always check logs after deployment to verify function behavior and troubleshoot issues.

Summary

Run 'firebase init functions' to create the Cloud Functions project files and setup.

Write your function code in the generated files inside the functions folder.

Deploy your functions to Firebase with 'firebase deploy --only functions' to make them live.

Use 'firebase functions:log' to view logs and verify your functions run correctly.

Practice

1. What is the first command you run to start setting up Cloud Functions in a Firebase project?

easy

A. firebase init functions

B. firebase deploy --only functions

C. firebase start functions

D. firebase create functions

Solution

1. Step 1: Understand Firebase setup commands

   The command firebase init functions initializes Cloud Functions in your project by creating necessary files and folders.

2. Step 2: Differentiate from deploy command

   firebase deploy --only functions is used after setup to upload your functions to Firebase, not to start setup.

3. Final Answer:

   firebase init functions -> Option A

4. Quick Check:

   Setup starts with firebase init functions [OK]

Hint: Setup always begins with 'firebase init functions' command [OK]

Common Mistakes:

• Confusing deploy command as setup
• Using non-existent commands like 'firebase start functions'
• Skipping initialization step

2. Which of the following is the correct way to deploy only Cloud Functions after writing your code?

easy

A. firebase deploy --only database

B. firebase deploy --only hosting

C. firebase deploy --only functions

D. firebase deploy --only storage

Solution

1. Step 1: Identify deployment targets

   Firebase allows deploying specific parts like hosting, functions, database, or storage using the --only flag.

2. Step 2: Match the correct target for Cloud Functions

   To deploy Cloud Functions only, use firebase deploy --only functions.

3. Final Answer:

   firebase deploy --only functions -> Option C

4. Quick Check:

   Deploy functions with --only functions [OK]

Hint: Use '--only functions' to deploy just Cloud Functions [OK]

Common Mistakes:

• Using wrong target like hosting or database
• Omitting '--only' and deploying everything
• Typing incorrect command syntax

3. Given this Cloud Function code snippet, what will happen when an HTTP request is made to it?

const functions = require('firebase-functions');
exports.helloWorld = functions.https.onRequest((request, response) => {
  response.send('Hello from Firebase!');
});

medium

A. The function does nothing and times out.

B. The function returns 'Hello from Firebase!' as the HTTP response.

C. The function throws an error because of missing return statement.

D. The function returns a JSON object with message 'Hello from Firebase!'.

Solution

1. Step 1: Understand the function trigger type

   This function uses functions.https.onRequest, which handles HTTP requests and sends responses.

2. Step 2: Analyze the response sent

   The function calls response.send('Hello from Firebase!'), which sends a plain text response with that message.

3. Final Answer:

   The function returns 'Hello from Firebase!' as the HTTP response. -> Option B

4. Quick Check:

   HTTP function sends plain text response [OK]

Hint: HTTP functions respond with response.send() text [OK]

Common Mistakes:

• Thinking response.send requires return
• Expecting JSON without using response.json()
• Assuming function times out without response

4. You wrote this Cloud Function but get an error when deploying:

exports.myFunction = functions.https.onRequest((req, res) => {
  res.send('Hi');
}

What is the problem?

medium

A. Missing closing parenthesis and semicolon after the function definition.

B. Using 'req' and 'res' instead of 'request' and 'response'.

C. The function name 'myFunction' is invalid.

D. Cloud Functions cannot handle HTTP requests.

Solution

1. Step 1: Check function syntax carefully

   The code snippet is missing a closing parenthesis ')' and semicolon ';' after the arrow function.

2. Step 2: Validate other parts

   Using 'req' and 'res' is valid parameter naming. Function name is valid. Cloud Functions support HTTP triggers.

3. Final Answer:

   Missing closing parenthesis and semicolon after the function definition. -> Option A

4. Quick Check:

   Syntax errors cause deployment failure [OK]

Hint: Check for missing brackets and semicolons in function code [OK]

Common Mistakes:

• Ignoring syntax errors like missing parentheses
• Thinking parameter names must be 'request' and 'response'
• Assuming Cloud Functions don't support HTTP

5. You want to create a Cloud Function that triggers when a new user is added to Firebase Authentication and logs their email. Which setup is correct?

hard

A. exports.logNewUser = functions.database.ref('/users/{userId}').onCreate((snapshot) => {
console.log('New user:', snapshot.val().email);
});

B. exports.logNewUser = functions.storage.object().onFinalize((object) => {
console.log('New user:', object.email);
});

C. exports.logNewUser = functions.https.onRequest((req, res) => {
console.log('New user:', req.body.email);
res.send('Logged');
});

D. exports.logNewUser = functions.auth.user().onCreate((user) => {
console.log('New user:', user.email);
});

Solution

1. Step 1: Identify the correct trigger for new Firebase Authentication users

   The trigger functions.auth.user().onCreate runs when a new user is created in Firebase Authentication.

2. Step 2: Confirm the logging of user email

   The callback receives a user object with an email property, which can be logged directly.

3. Step 3: Differentiate from other triggers

   Database triggers listen to database changes, HTTP triggers respond to requests, and storage triggers respond to file changes, so they are incorrect here.

4. Final Answer:

   Use auth user onCreate trigger to log new user email. -> Option D

5. Quick Check:

   Auth user onCreate triggers new user events [OK]

Hint: Use auth.user().onCreate for new Firebase Authentication users [OK]

Common Mistakes:

• Using database triggers for auth events
• Using HTTP triggers to detect user creation
• Confusing storage triggers with auth triggers