Custom events in Firebase - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

What happens when a Firebase custom event is logged without a required parameter?

You log a custom event in Firebase Analytics but omit a parameter marked as required in your app's event schema. What is the expected behavior?

Firebase

firebase.analytics().logEvent('purchase', {item_id: '12345'}); // missing 'value' parameter

A The event is logged successfully but the missing parameter is recorded as null.

B The event is rejected and not logged at all.

C The event is logged but flagged as invalid in the Firebase console.

D The event triggers an error in the client app and stops execution.

💡 Hint

Think about how Firebase Analytics handles optional and required parameters in custom events.

Firebase Analytics logs custom events even if some parameters are missing. Missing parameters are recorded as null or simply omitted, but the event itself is still logged.

❓ Configuration

intermediate

Which Firebase configuration is required to enable custom event tracking?

To track custom events in a Firebase app, which configuration step is mandatory?

A Add a custom event schema JSON file to the app source code.

B Enable Google Analytics in the Firebase project settings.

C Create a Cloud Function to listen for custom events.

D Set up a Firebase Realtime Database trigger for events.

💡 Hint

Consider what Firebase requires to collect and process analytics data.

Google Analytics must be enabled in the Firebase project to collect and view custom event data. Other options are unrelated to basic custom event tracking.

❓ Architecture

advanced

How to architect a Firebase system to react to custom events in real-time?

You want your Firebase app to perform actions immediately after a custom event is logged. Which architecture best supports this?

A Log events to Firestore and use Firestore triggers in Cloud Functions.

B Use Firebase Analytics to log events and Cloud Functions triggered by Analytics events.

C Send events to Firebase Realtime Database and poll for changes every minute.

D Use Firebase Hosting to serve a webhook endpoint that listens for events.

💡 Hint

Think about which Firebase services support real-time triggers on data changes.

Firebase Analytics events cannot directly trigger Cloud Functions. Logging events to Firestore allows Cloud Functions to react immediately to data changes via Firestore triggers.

❓ security

advanced

What is the best practice to secure custom event data sent from client apps?

To prevent malicious users from sending fake custom events to Firebase Analytics, what security measure should you implement?

A Validate event data on the client before sending and rely on Firebase security.

B Restrict event logging to authenticated users only.

C Encrypt event data in the client app before sending to Firebase Analytics.

D Use Firebase App Check to verify requests come from your authentic app instances.

💡 Hint

Consider Firebase's built-in tools to verify app integrity.

Firebase App Check helps ensure that only requests from your genuine app instances are accepted, reducing fake event submissions.

✅ Best Practice

expert

Which approach optimizes custom event naming and parameter usage for Firebase Analytics?

To maximize the usefulness and clarity of custom events in Firebase Analytics, which naming and parameter strategy is best?

A Create unique event names for every user action and avoid parameters to reduce complexity.

B Use event names with spaces and special characters for readability.

C Follow Firebase recommended event names and use typed parameters with clear names.

D Use short, generic event names and include all parameters as strings.

💡 Hint

Think about Firebase Analytics documentation recommendations for event design.

Firebase recommends using predefined event names when possible and using clear, typed parameters to improve analysis and reporting.

Practice

1. What is the main purpose of custom events in Firebase Analytics?

easy

A. To replace default events with simpler ones

B. To automatically collect user location data

C. To track specific user actions not covered by default events

D. To send notifications to users

Solution

1. Step 1: Understand default vs custom events

   Default events cover common actions, but some user actions need custom tracking.

2. Step 2: Identify the role of custom events

   Custom events let you track specific actions unique to your app that default events don't cover.

3. Final Answer:

   To track specific user actions not covered by default events -> Option C

4. Quick Check:

   Custom events = track unique user actions [OK]

Hint: Custom events track unique actions default events miss [OK]

Common Mistakes:

• Thinking custom events replace default events
• Assuming custom events send notifications
• Believing custom events collect location automatically

2. Which Firebase function is used to log a custom event with parameters?

easy

A. firebase.analytics().logEvent(eventName, params)

B. firebase.analytics().trackEvent(eventName, params)

C. firebase.analytics().sendEvent(eventName, params)

D. firebase.analytics().createEvent(eventName, params)

Solution

1. Step 1: Recall Firebase Analytics API for events

   The correct method to log events is logEvent.

2. Step 2: Confirm method signature

   logEvent takes the event name and optional parameters as arguments.

3. Final Answer:

   firebase.analytics().logEvent(eventName, params) -> Option A

4. Quick Check:

   logEvent = log custom events [OK]

Hint: Use logEvent to send custom events with parameters [OK]

Common Mistakes:

• Using trackEvent instead of logEvent
• Using sendEvent or createEvent which don't exist
• Confusing parameter order or names

3. What will happen if you run this code snippet?

firebase.analytics().logEvent('purchase', {item: 'book', price: 15});

medium

A. Throws a syntax error due to incorrect parameter format

B. Logs a custom event named 'purchase' with item and price parameters

C. Logs a default event ignoring parameters

D. Sends an error because 'purchase' is a reserved event name

Solution

1. Step 1: Analyze the logEvent call

   The code calls logEvent with event name 'purchase' and parameters object.

2. Step 2: Check if 'purchase' is valid and parameters are correct

   'purchase' is a valid event name and parameters are passed as an object correctly.

3. Final Answer:

   Logs a custom event named 'purchase' with item and price parameters -> Option B

4. Quick Check:

   logEvent('purchase', params) = logs event with params [OK]

Hint: logEvent with name and object logs event with parameters [OK]

Common Mistakes:

• Thinking 'purchase' is reserved and causes error
• Assuming parameters must be strings only
• Confusing syntax causing error

4. Identify the error in this Firebase custom event logging code:

firebase.analytics().logEvent('level_up', 'level', 5);

medium

A. Incorrect parameter format; parameters must be in an object

B. Event name must be uppercase

C. logEvent requires only one argument

D. The event name 'level_up' is invalid

Solution

1. Step 1: Review logEvent parameter requirements

   logEvent expects the second argument as an object containing key-value pairs.

2. Step 2: Identify the mistake in argument passing

   The code passes parameters as separate arguments instead of a single object.

3. Final Answer:

   Incorrect parameter format; parameters must be in an object -> Option A

4. Quick Check:

   Parameters must be an object, not separate arguments [OK]

Hint: Pass parameters as one object, not separate arguments [OK]

Common Mistakes:

• Passing parameters as multiple arguments
• Assuming event name case matters
• Thinking logEvent takes only one argument

5. You want to track when users complete a tutorial step with step number and success status. Which is the best way to log this custom event in Firebase?

hard

A. firebase.analytics().logEvent('tutorial_complete', {step: stepNumber, success: isSuccess});

B. firebase.analytics().logEvent('tutorial_complete', stepNumber, isSuccess);

C. firebase.analytics().logEvent('tutorialComplete', {stepNumber, isSuccess});

D. firebase.analytics().logEvent('tutorial_complete', {stepNumber: stepNumber, success: isSuccess});

Solution

1. Step 1: Check event name format

   Firebase recommends lowercase with underscores for event names, so 'tutorial_complete' is correct.

2. Step 2: Verify parameters object keys and values

   Parameters should be an object with clear keys. firebase.analytics().logEvent('tutorial_complete', {stepNumber: stepNumber, success: isSuccess}); uses keys 'stepNumber' and 'success' with values from variables.

3. Step 3: Compare options for best practice

   firebase.analytics().logEvent('tutorial_complete', {step: stepNumber, success: isSuccess}); uses 'step' key which is less descriptive than 'stepNumber'. firebase.analytics().logEvent('tutorialComplete', {stepNumber, isSuccess}); uses camelCase event name which is less recommended. firebase.analytics().logEvent('tutorial_complete', stepNumber, isSuccess); passes parameters incorrectly.

4. Final Answer:

   firebase.analytics().logEvent('tutorial_complete', {stepNumber: stepNumber, success: isSuccess}); -> Option D

5. Quick Check:

   Use descriptive keys and correct event name format [OK]

Hint: Use descriptive keys and underscore event names [OK]

Common Mistakes:

• Passing parameters as separate arguments
• Using camelCase event names instead of underscores
• Using unclear parameter keys