Creating Mapped Types

type Album = {
	title: string
	year: number
}

type Optional<T> = { [K in keyof T]?: T[K] }
type OptionalAlbum = Optional<Album>

1. Recreate Partial<T> from scratch
2. Recreate Required<T> from scratch
3. Create a Nullable<T> that makes all properties nullable
4. Create a Mutable<T> that removes readonly