Why type aliases are needed in Typescript - Test Your Understanding

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];

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Aboolean

Bstring

Cnumber

Dany

Attempts:

3 left

💡 Hint

Common Mistakes

Using a value like 5 instead of a type like number.

Confusing type aliases with variables.

The type keyword creates a type alias. Here, Age is an alias for number.

2fill in blank

medium

Complete the code to define a type alias Point for an object with x and y as numbers.

Typescript

type Point = [1];

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A{ x: number; y: number }

B{ x: string; y: string }

C[number, number]

Dnumber

Attempts:

3 left

💡 Hint

Common Mistakes

Using strings instead of numbers for coordinates.

Using an array type instead of an object.

The type alias Point describes an object with two properties, x and y, both numbers.

3fill in blank

hard

Fix the error by completing the type alias for a union of string literals representing directions.

Typescript

type Direction = [1];

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Aup | down | left | right

B"up" | "down" | "left" | "right"

Cstring

Dnumber

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving out quotes around string literals.

Using variable names instead of string literals.

Union types use the pipe | to combine string literals. Quotes are needed around each string.

4fill in blank

hard

Fill all three blanks to create a type alias Response that can be either a string or a number.

Typescript

type Response = [1] [2] [3];

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Astring

B|

Cnumber

D&

Attempts:

3 left

💡 Hint

Common Mistakes

Using & instead of | for union.

Forgetting to separate types with |.

The union type uses | to allow Response to be either string or number.

5fill in blank

hard

Fill all three blanks to create a type alias User for an object with id as number, name as string, and an optional age as number.

Typescript

type User = { id: [1]; name: [2]; age?: [3]; };

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

Astring

Bnumber

Cboolean

Dany

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong types for properties.

Forgetting the optional marker ?.

The User type has id and optional age as numbers, and name as a string. The question mark ? marks age as optional.