Event handling in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the EventEmitter2 class from NestJS.

NestJS

import { [1] } from '@nestjs/event-emitter';

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AEventDispatcher

BEventHandler

CEventListener

DEventEmitter2

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect class names like EventHandler or EventListener.

Forgetting to import from '@nestjs/event-emitter'.

The EventEmitter2 class is imported from @nestjs/event-emitter to handle events in NestJS.

2fill in blank

medium

Complete the code to inject the EventEmitter2 into the service constructor.

NestJS

constructor(private readonly [1]: EventEmitter2) {}

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AeventEmitter

BeventHandler

CeventListener

DeventDispatcher

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect property names that do not match the class.

Forgetting the private readonly keywords.

The injected property should be named eventEmitter to clearly represent the EventEmitter2 instance.

3fill in blank

hard

Fix the error in emitting an event with a payload.

NestJS

this.eventEmitter.[1]('user.created', { id: 1, name: 'Alice' });

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AemitEvent

Bdispatch

Cemit

Dtrigger

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like emitEvent or dispatch.

Confusing with other event libraries.

The correct method to emit an event in NestJS EventEmitter2 is emit.

4fill in blank

hard

Fill both blanks to create an event listener method that listens to 'order.placed' events.

NestJS

@[1]('order.placed')
handleOrderPlaced([2]: any) {
  console.log('Order received:', [2]);
}

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AOnEvent

BEventHandler

Corder

Dpayload

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect decorator names like @EventHandler.

Using unclear parameter names.

The @OnEvent decorator listens to events, and the method parameter is commonly named payload to hold event data.

5fill in blank

hard

Fill all three blanks to emit an event and handle it properly in NestJS.

NestJS

this.[1].[2]('payment.completed', { amount: 100 });

@[3]('payment.completed')
handlePaymentCompleted(payload: any) {
  console.log('Payment done:', payload.amount);
}

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

AeventEmitter

Bemit

COnEvent

Ddispatch

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong method names like 'dispatch'.

Using wrong decorator names.

Use eventEmitter.emit to send events and @OnEvent decorator to listen to them.