Why providers encapsulate business logic in NestJS - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to inject a provider into a controller.

NestJS

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

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

AUsersService

BuserService

CusersService

DUserService

Attempts:

3 left

💡 Hint

Common Mistakes

Using the class name with uppercase as the property name

Misspelling the service name

The provider instance is injected using a private readonly property with camelCase naming.

2fill in blank

medium

Complete the code to call a method from the provider inside a controller method.

NestJS

return this.usersService.[1](id);

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

AfindUserById

BcreateUser

CdeleteUser

DupdateUser

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a method that creates or deletes instead of fetching

Using a method name that does not exist in the provider

The controller calls the provider method that fetches a user by ID.

3fill in blank

hard

Fix the error in the provider method signature to properly return a Promise.

NestJS

async getUser(id: string): [1] {

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

AObservable<User>

BUser

Cvoid

DPromise<User>

Attempts:

3 left

💡 Hint

Common Mistakes

Returning the type directly without Promise

Using void or Observable instead of Promise

Async methods in NestJS providers should return a Promise of the expected type.

4fill in blank

hard

Fill both blanks to create a provider method that filters users by age.

NestJS

getUsersByAge([1]: number): User[] {
  return this.users.filter(user => user.[2] === age);
}

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

Aage

BageLimit

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for parameter and property causing errors

Using undefined variable names

The method parameter and the user property to compare must both be 'age' to filter correctly.

5fill in blank

hard

Fill all three blanks to create a provider method that returns a dictionary of user names keyed by their IDs for users older than 18.

NestJS

getAdultUserNames(): Record<string, string> {
  return this.users.reduce((acc, user) => {
    if (user.[1] > [2]) {
      acc[user.[3]] = user.name;
    }
    return acc;
  }, {});
}

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

Aage

B18

Cid

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong property for the key in the dictionary

Comparing with incorrect age value

The method checks if user age is greater than 18 and uses user id as the key in the result object.