HTTP trigger functions in Firebase - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this Firebase HTTP trigger function?

Consider this Firebase HTTP trigger function code snippet:

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

What will the client receive when making a GET request to this function?

Firebase

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

A The client receives an error because the function does not return a promise.

B The client receives a JSON object {message: 'Hello from Firebase!'} as the response body.

C The client receives an empty response with status 200.

D The client receives the string 'Hello from Firebase!' as the response body.

💡 Hint

Look at what the response.send() method sends back.

The response.send() method sends the exact string as the HTTP response body. Here, it sends 'Hello from Firebase!'.

📝 Syntax

intermediate

Identify the syntax error in this Firebase HTTP trigger function

Which option contains the correct syntax for defining a Firebase HTTP trigger function?

Firebase

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

A

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

B

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

C

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

D

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

💡 Hint

Check the arrow function syntax and parentheses.

The correct syntax uses functions.https.onRequest((req, res) => { ... }) with parentheses around parameters and the arrow function inside.

❓ optimization

advanced

Which option optimizes response time for a Firebase HTTP trigger function?

You want your Firebase HTTP trigger function to respond quickly without waiting for asynchronous tasks. Which option achieves this?

Firebase

exports.fastResponse = functions.https.onRequest(async (req, res) => {
  // Some async task
  await someAsyncTask();
  res.send('Done');
});

A Remove <code>await</code> and call <code>someAsyncTask()</code> without waiting, then send response immediately.

B Use <code>setTimeout</code> to delay the response by 2 seconds.

C Keep <code>await</code> so the function waits for the async task before responding.

D Return a promise that never resolves to keep the function alive.

💡 Hint

Think about sending the response without waiting for the async task.

Removing await lets the function send the response immediately, improving response time. The async task runs in the background.

🧠 Conceptual

advanced

What happens if a Firebase HTTP trigger function does not send a response?

If a Firebase HTTP trigger function does not call response.send() or similar methods, what will happen?

A The function logs an error but sends a 200 OK response.

B Firebase automatically sends a default success response.

C The client request will hang until timeout because no response is sent.

D The function throws a syntax error immediately.

💡 Hint

Think about what happens when a server never replies to a request.

If no response is sent, the client waits until the request times out, causing a hanging request.

🔧 Debug

expert

Why does this Firebase HTTP trigger function cause a timeout error?

Examine this function:

exports.timeoutFunc = functions.https.onRequest((req, res) => {
  someAsyncOperation();
  // Missing response.send or end
});

Why does this cause a timeout error?

A Because the function never sends a response, the client waits indefinitely until timeout.

B Because <code>someAsyncOperation()</code> is not awaited, it causes a syntax error.

C Because <code>response.send()</code> is called twice causing a conflict.

D Because the function returns a promise that rejects immediately.

💡 Hint

Check if the function sends any response back to the client.

The function calls an async operation but never sends a response. This causes the client to wait until timeout.