Error events and handling in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the 'error' event in Node.js EventEmitter?

The 'error' event signals that an error has occurred in an EventEmitter. If not handled, it causes the program to crash. Handling this event lets you manage errors gracefully.

beginner

How do you listen for an 'error' event on a Node.js stream?

Use the .on('error', callback) method on the stream object. The callback receives the error object to handle it properly.

intermediate

What happens if an 'error' event is emitted but no listener is attached?

Node.js throws an uncaught 'error' event which crashes the program. Always attach an 'error' listener to avoid unexpected crashes.

intermediate

Explain the difference between synchronous try-catch and 'error' event handling in Node.js.

Try-catch handles errors in synchronous code blocks. 'error' event handling manages asynchronous errors emitted by EventEmitters like streams or servers.

beginner

Why is it important to handle 'error' events in Node.js applications?

Handling 'error' events prevents the app from crashing unexpectedly. It allows you to log errors, clean up resources, and provide user-friendly feedback.

What method do you use to listen for an 'error' event on an EventEmitter?

A .on('error', callback)

B .catch('error', callback)

C .listen('error', callback)

D .handle('error', callback)

The correct method is .on('error', callback) to listen for error events.

What happens if an 'error' event is emitted but no listener is attached?

A The error is ignored silently

B The program logs a warning but continues

C The event is queued for later

D Node.js throws and crashes the program

Without an 'error' listener, Node.js throws an uncaught error and crashes.

Which of these is NOT a correct way to handle errors in Node.js?

A Ignoring errors and continuing

B Listening to 'error' events on streams

C Using try-catch for synchronous code

D Using promises with .catch() for async errors

Ignoring errors can cause crashes or bugs; always handle errors properly.

In Node.js, which object commonly emits 'error' events?

A String

B Array

C EventEmitter

D Number

EventEmitter and its subclasses like streams emit 'error' events.

Why should you handle 'error' events on streams?

A To prevent memory leaks

B To avoid program crashes

C To improve performance

D To enable debugging mode

Handling 'error' events prevents crashes caused by unhandled errors.

Describe how error events work in Node.js and why handling them is important.

Think about what happens if errors are not caught in event-driven code.

Explain the difference between synchronous error handling and error event handling in Node.js.

Consider how Node.js handles errors in different code types.