Resource and request objects in Firebase - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to access the resource object in a Firebase Cloud Function.

Firebase

exports.myFunction = functions.https.onRequest(([1], response) => {
  response.send('Hello World');
});

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

Arequest

Bresource

Cevent

Dreq

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'resource' instead of 'req' as the first parameter.

Naming the first parameter 'response' instead of 'req'.

The first parameter in an HTTPS Cloud Function is the request object, commonly named req.

2fill in blank

medium

Complete the code to send a JSON response using the response object.

Firebase

exports.myFunction = functions.https.onRequest((req, [1]) => {
  [1].json({ message: 'Success' });
});

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

Arequest

Bresponse

Cres

Devent

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'request' instead of 'response' as the second parameter.

Using 'response' but calling the variable 'req'.

The second parameter is the response object, commonly named res, used to send data back.

3fill in blank

hard

Fix the error in accessing a property from the request object.

Firebase

exports.myFunction = functions.https.onRequest((req, res) => {
  const userId = req.[1].userId;
  res.send(`User ID is ${userId}`);
});

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

Abody

Bparams

Cquery

Dresource

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'params' when the data is in the request body.

Using 'query' for POST request data.

The body property contains data sent in the request payload, including userId.

4fill in blank

hard

Fill both blanks to extract a path parameter and send it in the response.

Firebase

exports.myFunction = functions.https.onRequest((req, res) => {
  const itemId = req.[1].itemId;
  res.[2](`Item ID: ${itemId}`);
});

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

Aparams

Bsend

Cbody

Djson

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'body' to get path parameters.

Using 'json' instead of 'send' for plain text.

Path parameters are accessed via req.params. The response is sent using res.send().

5fill in blank

hard

Fill all three blanks to correctly read a query parameter, check its value, and respond accordingly.

Firebase

exports.myFunction = functions.https.onRequest((req, res) => {
  const action = req.[1].action;
  if (action === '[2]') {
    res.[3]({ result: 'Action received' });
  } else {
    res.status(400).send('Invalid action');
  }
});

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

Aquery

Bstart

Cjson

Dbody

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'body' instead of 'query' for URL parameters.

Sending plain text instead of JSON response.

Query parameters are accessed via req.query. We check if action equals 'start' and respond with JSON using res.json().

Practice

1. What does a request object in Firebase functions mainly contain?

easy

A. Logs of previous function executions

B. Details about the data or file that triggered the function

C. Settings for Firebase project configuration

D. Information about what the user sent and how

Solution

1. Step 1: Understand the role of request objects

   The request object holds details about the user's input and request method.

2. Step 2: Differentiate from resource objects

   Resource objects describe the trigger data or file, not user input.

3. Final Answer:

   Information about what the user sent and how -> Option D

4. Quick Check:

   Request object = user input info [OK]

Hint: Request = user input details, Resource = trigger data [OK]

Common Mistakes:

• Confusing resource object with request object
• Thinking request holds trigger file info
• Assuming request contains project settings

2. Which of the following is the correct way to access the data sent by a user in a Firebase HTTPS function's request object?

easy

A. request.data.body

B. request.body.data

C. request.payload

D. request.trigger.data

Solution

1. Step 1: Recall request object structure

   In Firebase HTTPS functions, user data is inside request.body.

2. Step 2: Identify correct property for user data

   The user data is accessed as request.body.data if data is nested inside body.

3. Final Answer:

   request.body.data -> Option B

4. Quick Check:

   Access user data via request.body.data [OK]

Hint: User data is inside request.body in HTTPS functions [OK]

Common Mistakes:

• Using request.data.body which is invalid
• Trying to access request.payload which doesn't exist
• Confusing trigger data with request data

3. Given this Firebase function snippet:

exports.myFunction = functions.storage.object().onFinalize((object, context) => {
  console.log(object.name);
  console.log(context.eventId);
});

What does the object parameter represent?

medium

A. The Firebase project configuration

B. The user's HTTP request data

C. The file that triggered the function

D. The function's execution logs

Solution

1. Step 1: Identify the trigger type

   The function triggers on a storage object finalization, meaning a file event.

2. Step 2: Understand the object parameter

   The object parameter holds info about the file that triggered the function.

3. Final Answer:

   The file that triggered the function -> Option C

4. Quick Check:

   Storage trigger object = file info [OK]

Hint: Storage triggers pass file info as object parameter [OK]

Common Mistakes:

• Thinking object is user request data
• Confusing context with resource object
• Assuming object holds config or logs

4. Identify the error in this Firebase HTTPS function code:

exports.func = functions.https.onRequest((resource, request) => {
  console.log(request.body);
});

medium

A. Parameters are reversed; should be (request, response)

B. Missing return statement

C. Incorrect function name

D. No error; code is correct

Solution

1. Step 1: Check HTTPS function parameters

   HTTPS functions receive (request, response) parameters in that order.

2. Step 2: Identify parameter misuse

   The code uses (resource, request) which reverses and misnames parameters.

3. Final Answer:

   Parameters are reversed; should be (request, response) -> Option A

4. Quick Check:

   HTTPS function params = (request, response) [OK]

Hint: HTTPS functions always use (request, response) parameters [OK]

Common Mistakes:

• Swapping request and response parameters
• Using resource parameter in HTTPS function
• Ignoring parameter order importance

5. You want to write a Firebase function triggered by Firestore document changes. Which object should you use to access the changed document's data inside the function?

hard

A. resource.after.data()

B. request.body

C. context.params

D. resource.data()

Solution

1. Step 1: Understand Firestore trigger parameters

   Firestore triggers receive a change object with before and after snapshots.

2. Step 2: Access the new document data

   The updated document data is accessed via change.after.data(), which is the resource object.

3. Final Answer:

   resource.after.data() -> Option A

4. Quick Check:

   Firestore change after data = resource.after.data() [OK]

Hint: Use resource.after.data() for updated Firestore document data [OK]

Common Mistakes:

• Using request.body which is for HTTP functions
• Using context.params which holds path variables
• Using resource.data() which is old snapshot, not updated