Creating type aliases in Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a type alias named Age for the number type.

Typescript

type Age = [1];

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

Anumber

Bstring

Cboolean

Dany

Attempts:

3 left

💡 Hint

Common Mistakes

Using string instead of number.

Forgetting the semicolon at the end.

The Age type alias should represent the number type, so we write type Age = number;.

2fill in blank

medium

Complete the code to create a type alias named Coordinates for an object with x and y properties of type number.

Typescript

type Coordinates = [1];

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

A{ x: string; y: string }

B{ x: number; y: number }

C[number, number]

Dnumber[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using string types for x and y.

Using an array instead of an object.

The Coordinates type alias should be an object with x and y as numbers, so we write { x: number; y: number }.

3fill in blank

hard

Fix the error in the type alias declaration for Person which should have a name string and an optional age number.

Typescript

type Person = { name: string; age[1]: number };

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

A;

B:

C?

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using colon instead of question mark for optional property.

Missing the question mark causes age to be required.

To make age optional, use a question mark after the property name: age?: number.

4fill in blank

hard

Fill both blanks to create a type alias ID that can be either a string or a number.

Typescript

type ID = [1] | [2];

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

Astring

Bnumber

Cboolean

Dobject

Attempts:

3 left

💡 Hint

Common Mistakes

Using boolean or object instead of string or number.

Forgetting the pipe symbol.

The ID type alias should allow either string or number, so use a union type: string | number.

5fill in blank

hard

Fill all three blanks to create a type alias Response for an object with a status string, a data array of numbers, and an optional error string.

Typescript

type Response = { status: [1]; data: [2]; error[3]: string };

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

Astring

Bnumber[]

C?

Dboolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using boolean instead of string for status.

Forgetting the question mark for the optional error property.

The status is a string, data is an array of numbers (number[]), and error is optional, so it uses a question mark.