Custom event emitter classes in Node.js - Interactive Code Practice

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 incorrect class names like 'Emitter' or 'Event'.

Forgetting to require the 'events' module.

The EventEmitter class is imported from the 'events' module using const EventEmitter = require('events');.

2fill in blank

medium

Complete the code to create a new class named MyEmitter that extends EventEmitter.

Node.js

class MyEmitter extends [1] {
  constructor() {
    super();
  }
}

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

AEmitter

BEventEmitter

CEvent

DEmitterClass

Attempts:

3 left

💡 Hint

Common Mistakes

Extending a wrong or undefined class.

Forgetting to call super() in the constructor.

The custom class should extend EventEmitter to inherit event capabilities.

3fill in blank

hard

Fix the error in the code to emit a 'start' event from the emitter instance.

Node.js

const emitter = new MyEmitter();
emitter.[1]('start');

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Aemit

Bfire

CemitEvent

Dtrigger

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like 'trigger' or 'fire'.

Using 'emitEvent' which is not a method.

The correct method to emit an event is emit.

4fill in blank

hard

Fill both blanks to add a listener for the 'data' event that logs the received message.

Node.js

emitter.[1]('data', ([2]) => {
  console.log([2]);
});

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

Aon

Bmessage

Cdata

Dlisten

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'addListener' instead of 'on' (valid but not in options).

Using the event name as the parameter name.

The on method adds a listener, and the parameter name can be any valid identifier like 'message'.

5fill in blank

hard

Fill all three blanks to create an instance, add a listener for 'end', and emit the 'end' event.

Node.js

const [1] = new MyEmitter();
[1].on('end', () => {
  console.log('Finished');
});
[1].[2]('end');

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

Aemitter

Bemit

Ctrigger

Dfire

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong method names like 'trigger' or 'fire'.

Using different variable names inconsistently.

Create an instance named 'emitter', use on to add a listener, and emit to trigger the event.