Type alias for unions in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a type alias named Result that can be either a string or a number.

Typescript

type Result = [1];

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Astring & number

Bstring, number

Cstring number

Dstring | number

Attempts:

3 left

💡 Hint

Common Mistakes

Using & instead of | which means intersection, not union.

Separating types with a comma instead of |.

The | symbol creates a union type, so string | number means the type can be either a string or a number.

2fill in blank

medium

Complete the code to define a type alias Status that can be either 'success' or 'error'.

Typescript

type Status = [1];

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A'success' 'error'

B'success' | 'error'

C'success', 'error'

D'success' & 'error'

Attempts:

3 left

💡 Hint

Common Mistakes

Using & which means intersection and is not valid for string literals here.

Separating with commas or spaces instead of |.

Using | creates a union of string literal types, allowing Status to be either 'success' or 'error'.

3fill in blank

hard

Fix the error in the type alias Input so it correctly represents a union of boolean or number.

Typescript

type Input = boolean [1] number;

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

A|

B&

C,

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using & which means intersection, not union.

Using commas or slashes which are invalid here.

The union operator | correctly combines boolean and number types.

4fill in blank

hard

Fill both blanks to define a type alias Response that can be either a string or an array of numbers.

Typescript

type Response = [1] | [2];

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Astring

Bnumber[]

Cboolean

Dobject

Attempts:

3 left

💡 Hint

Common Mistakes

Using boolean or object instead of the correct types.

Forgetting the union operator |.

The type Response can be a string or an array of numbers number[].

5fill in blank

hard

Fill all three blanks to define a type alias Data that can be a string, number, or an array of booleans.

Typescript

type Data = [1] | [2] | [3];

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

Astring

Bnumber

Cboolean[]

Dobject

Attempts:

3 left

💡 Hint

Common Mistakes

Including object which is not part of the union.

Using intersection & instead of union |.

The type Data can be a string, a number, or an array of booleans boolean[].