Ambient declarations in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an ambient variable named myVar of type string.

Typescript

declare var [1]: string;

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

AvarName

BmyVariable

CmyVar

Dvariable

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different variable name than myVar.

Trying to assign a value instead of declaring.

The declare var syntax is used to declare an ambient variable. Here, myVar is the variable name.

2fill in blank

medium

Complete the code to declare an ambient function named greet that takes a name parameter of type string and returns void.

Typescript

declare function [1](name: string): void;

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Agreet

BsayHello

Chello

Dwelcome

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name.

Adding a function body instead of just declaring.

The ambient function declaration uses declare function followed by the function name. Here, the function name is greet.

3fill in blank

hard

Fix the error in the ambient declaration by completing the code to declare a constant named PI of type number.

Typescript

declare const [1]: number;

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

ApiValue

BPI

Cpi

DPi

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or mixed case names.

Trying to assign a value in ambient declarations.

Ambient constants are declared with declare const. The name must match exactly PI (case-sensitive).

4fill in blank

hard

Fill both blanks to declare an ambient namespace named Utils with a function log that takes a message string and returns void.

Typescript

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

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

AUtils

BLogger

Clog

Dprint

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong namespace or function names.

Trying to add function bodies inside ambient declarations.

The ambient namespace is declared with declare namespace Utils. Inside it, the function log is declared.

5fill in blank

hard

Fill all three blanks to declare an ambient interface named Person with a name property of type string and an optional age property of type number.

Typescript

declare interface [1] {
  [2]: string;
  [3]?: number;
}

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

APerson

Bname

Cage

DUser

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong interface or property names.

Missing the optional property marker ?.

The ambient interface is declared with declare interface Person. It has a required name property and an optional age property.