Why the event system matters in Node.js - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the EventEmitter class from the 'events' module.

Node.js

const [1] = require('events');

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

AEventEmitter

BEmitter

CEvent

DEmitterClass

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong class name like 'Emitter' or 'Event'.

Forgetting to import the class before using it.

The EventEmitter class is the core of Node.js event system. Importing it correctly allows you to create event-driven code.

2fill in blank

medium

Complete the code to create a new instance of EventEmitter.

Node.js

const emitter = new [1]();

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

AEventEmitter

BEmitter

CEvent

DEmitterClass

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to instantiate a wrong or undefined class.

Using lowercase or misspelled class names.

You create a new event emitter by calling new EventEmitter(). This instance can then emit and listen to events.

3fill in blank

hard

Fix the error in the code to listen for the 'message' event.

Node.js

emitter.[1]('message', () => {
  console.log('Message received');
});

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Alisten

BaddListenerEvent

ConMessage

Don

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like 'listen' or 'onMessage'.

Confusing event registration with event emitting.

The correct method to listen for events in Node.js EventEmitter is on. It registers a callback for the named event.

4fill in blank

hard

Fill both blanks to emit a 'data' event with a payload.

Node.js

emitter.[1]('[2]', { id: 1, value: 'hello' });

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Aemit

Bdata

Csend

Dmessage

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'send' instead of 'emit' to trigger events.

Using wrong event names that don't match listeners.

To send an event, use emit with the event name and data. Here, the event name is 'data'.

5fill in blank

hard

Fill all three blanks to create a listener for 'update' event that logs the payload's status.

Node.js

emitter.[1]('[2]', (payload) => {
  console.log('Status:', payload.[3]);
});

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

Aon

Bupdate

Cstatus

Demit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'emit' instead of 'on' to listen for events.

Using wrong event names or property names.

Use on to listen for the 'update' event. The callback receives a payload object, and we access its 'status' property.