HTTP trigger functions in Firebase - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an HTTP trigger function in Firebase?

An HTTP trigger function is a cloud function that runs when it receives an HTTP request. It lets you handle web requests like a web server.

beginner

How do you define an HTTP trigger function in Firebase?

You define it using functions.https.onRequest((req, res) => { ... }). This sets up a function that runs when an HTTP request is made.

beginner

What are the two main objects passed to an HTTP trigger function handler?

The two objects are req (request) and res (response). req has info about the incoming request, and res is used to send back a response.

intermediate

Why would you use an HTTP trigger function instead of a regular Firebase function?

Because HTTP trigger functions let you create APIs or webhooks that respond to web requests directly, making your backend accessible over the internet.

beginner

How do you send a JSON response from an HTTP trigger function?

Use res.json({ key: 'value' }) to send a JSON object back to the client.

Which method defines an HTTP trigger function in Firebase?

A functions.database.onWrite()

B functions.auth.user().onCreate()

C functions.https.onRequest()

D functions.storage.onFinalize()

Only functions.https.onRequest() sets up an HTTP trigger function.

What does the res object do in an HTTP trigger function?

A Contains info about the incoming request

B Sends a response back to the client

C Triggers the function execution

D Stores data in the database

res is used to send back responses like text or JSON.

How do you send a plain text response in an HTTP trigger function?

A req.send('text')

B res.json('text')

C req.json('text')

D res.send('text')

res.send() sends plain text or HTML responses.

Which of these is NOT a typical use case for HTTP trigger functions?

A Responding to database changes

B Serving dynamic web content

C Handling webhooks

D Creating REST APIs

Responding to database changes uses database triggers, not HTTP triggers.

What happens if you don't send a response in an HTTP trigger function?

A The function times out and the client waits indefinitely

B The function automatically sends a default response

C The function logs an error but returns success

D The function restarts automatically

Without sending a response, the client waits until the function times out.

Explain how an HTTP trigger function works in Firebase and what objects it uses.

Think about how a web server handles requests and responses.

Describe a simple example of when you would use an HTTP trigger function in a Firebase project.

Imagine you want to let a website or app ask your backend for data.