Unhandled rejection handling in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to listen for unhandled promise rejections.

Node.js

process.on('unhandledRejection', [1] => {
  console.error('Unhandled rejection:', [1]);
});

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

Ae

Berr

Creason

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Using a parameter name that is not descriptive like 'e' or 'err' can confuse the purpose.

Not handling the event at all causes the process to crash on unhandled rejections.

The event listener for 'unhandledRejection' receives the reason why the promise was rejected.

2fill in blank

medium

Complete the code to exit the process after logging an unhandled rejection.

Node.js

process.on('unhandledRejection', reason => {
  console.error('Unhandled rejection:', reason);
  process.[1](1);
});

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

Aexit

Bquit

Cstop

Dend

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like 'stop' or 'quit' causes runtime errors.

Not exiting the process may leave the app in an unstable state.

Use process.exit(1) to stop the Node.js process with an error code after an unhandled rejection.

3fill in blank

hard

Fix the error in the unhandled rejection handler to correctly log the error stack.

Node.js

process.on('unhandledRejection', (reason) => {
  console.error('Error stack:', [1]);
});

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

Areason.toString()

Breason.error

Creason.message

Dreason.stack

Attempts:

3 left

💡 Hint

Common Mistakes

Logging 'reason.message' instead of 'reason.stack' loses debugging details.

Accessing a non-existent property like 'reason.error' causes undefined output.

The stack property of the error object shows the full stack trace for debugging.

4fill in blank

hard

Fill both blanks to create a handler that logs the error and then exits the process.

Node.js

process.on('unhandledRejection', ([1]) => {
  console.error('Unhandled rejection:', [2]);
  process.exit(1);
});

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

Areason

Berror

Cerr

De

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the parameter and the logged variable causes reference errors.

Using generic names like 'e' can reduce code readability.

Using the same parameter name reason consistently helps clarity and correctness.

5fill in blank

hard

Fill all three blanks to create a robust unhandled rejection handler that logs the error stack, warns, and exits.

Node.js

process.on('unhandledRejection', ([1]) => {
  console.error('Unhandled rejection stack:', [2]);
  console.warn('Warning: process will exit due to unhandled rejection');
  process.[3](1);
});

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

Areason

Breason.stack

Cexit

Derr

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'err' instead of 'reason' can confuse the event parameter.

Logging 'reason' instead of 'reason.stack' loses stack trace info.

Calling a non-existent method instead of 'exit' causes runtime errors.

The handler uses reason as the parameter, logs reason.stack for details, and calls process.exit(1) to stop the app.