Type Lookup

In this medium-level challenge, you'll implement the LookUp<U, T> type, that looks up a type in a union by its attributes. This is especially useful when you are working with discriminated unions.

interface Cat {
type: 'cat'
breeds: 'Abyssinian' | 'Shorthair' | 'Curl' | 'Bengal'
}
 
interface Dog {
type: 'dog'
breeds: 'Hound' | 'Brittany' | 'Bulldog' | 'Boxer'
color: 'brown' | 'white' | 'black'
}
 
type MyDogType = LookUp<Cat | Dog, 'dog'> // expected to be `Dog`

Detailed Explanation

type LookUp<U, T> = U extends { type: T } ? U : never

How it works:

• We use a conditional type to check if U extends { type: T }.
• If it does, we return U, otherwise we return never.
• This is a simple way to look up a type in a union by its attributes.

This challenge helps you understand union type manipulation and how to apply this concept in real-world scenarios.