Writing custom declaration files in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a module named 'myLib'.

Typescript

declare module [1] {
  export function greet(name: string): string;
}

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

A'library'

B'lib'

C'myLib'

D'myLibrary'

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put the module name in quotes.

Using a different module name than 'myLib'.

The module name must be exactly 'myLib' as specified.

2fill in blank

medium

Complete the code to declare a variable 'version' of type string inside the module.

Typescript

declare module 'myLib' {
  export const [1]: string;
}

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

Aversion

Bver

Cv

DverNum

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different variable name than 'version'.

Putting the variable name in quotes.

The variable name must be 'version' as specified.

3fill in blank

hard

Fix the error in the declaration of a function 'add' that takes two numbers and returns a number.

Typescript

declare module 'myLib' {
  export function add(a: number, b: number)[1] number;
}

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

A=>

B=

C->

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=>' instead of ':'.

Using '=' or '->' which are invalid here.

In TypeScript declaration files, the return type is specified with a colon ':'.

4fill in blank

hard

Fill both blanks to declare an interface 'User' with a string property 'name' and a number property 'age'.

Typescript

declare module 'myLib' {
  export interface [1] {
    name: string;
    [2]: number;
  }
}

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

AUser

Busername

Cage

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong interface or property names.

Confusing property names with variable names.

The interface name is 'User' and the number property is 'age'.

5fill in blank

hard

Fill both blanks to declare a namespace 'Utils' with a function 'log' that takes a string and returns void.

Typescript

declare namespace [1] {
  export function [2](message: string): void;
}

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

AUtils

Blog

C:

DLogger

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong namespace or function names.

Using '=>' instead of ':' for return type.

The namespace is 'Utils', function name is 'log', and return type uses ':'.