TypeScript-first philosophy in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a NestJS controller using TypeScript decorators.

NestJS

import { Controller, Get } from '@nestjs/common';

@Controller('[1]')
export class AppController {
  @Get()
  getHello(): string {
    return 'Hello World!';
  }
}

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

Aapp

BAppController

Chello

Droot

Attempts:

3 left

💡 Hint

Common Mistakes

Using the class name instead of a route string.

Leaving the decorator empty which defaults to root.

The @Controller decorator takes a string that defines the route path. Here, 'app' sets the base route for this controller.

2fill in blank

medium

Complete the code to inject a service into a NestJS controller constructor.

NestJS

import { Controller } from '@nestjs/common';
import { AppService } from './app.service';

@Controller('app')
export class AppController {
  constructor(private readonly [1]: AppService) {}
}

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AappService

BAppService

Cappservice

Dservice

Attempts:

3 left

💡 Hint

Common Mistakes

Using the class name with uppercase first letter as variable name.

Using a generic name like 'service' which is unclear.

By convention, the injected service is named in camelCase matching the class name, here appService.

3fill in blank

hard

Fix the error in the following NestJS service method signature by completing the return type.

NestJS

import { Injectable } from '@nestjs/common';

@Injectable()
export class AppService {
  getData(): [1] {
    return { message: 'Data fetched' };
  }
}

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Aany

Bobject

Cstring

DRecord<string, string>

Attempts:

3 left

💡 Hint

Common Mistakes

Using string which is incorrect for an object return.

Using any which loses type safety.

The method returns an object with string keys and string values, so Record<string, string> is the precise TypeScript type.

4fill in blank

hard

Fill both blanks to create a NestJS DTO class with two properties having types and decorators.

NestJS

import { IsString, IsInt } from 'class-validator';

export class CreateUserDto {
  @[1]()
  name: string;

  @[2]()
  age: number;
}

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AIsString

BIsNumber

CIsInt

DIsBoolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using IsNumber for age which allows floats.

Using IsBoolean which is wrong type.

IsString validates that name is a string, and IsInt validates that age is an integer number.

5fill in blank

hard

Fill all three blanks to complete a NestJS module importing a service and controller.

NestJS

import { Module } from '@nestjs/common';
import { [1] } from './app.service';
import { [2] } from './app.controller';

@Module({
  imports: [],
  controllers: [[3]],
  providers: [AppService],
})
export class AppModule {}

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AAppService

BAppController

DAppModule

Attempts:

3 left

💡 Hint

Common Mistakes

Using the module class name in imports or controllers.

Forgetting to add the controller to the controllers array.

The module imports AppService and AppController. The controller is listed in the controllers array.