Create Type that consists of readonly properties from imported classes

given classes like the following

class Dog {
   public readonly key:string = 'dog'
}

class Cat {
   public readonly key:string = 'cat'
}

export default [new Dog(), new Cat()]

is it possible to import those into another file, treat them as a const, and derive a type from their key?

import animals from '...'

type AnimalKeys = typeof animals[number]['key'] // type string

the type AnimalKeys is string. I'm hoping for the type to be 'dog' | 'cat'

playground

Solution 1:

Don't type them as a string.

class Dog {
   public readonly key = 'dog' as const
}

class Cat {
   public readonly key = 'cat' as const
}

const animals = [new Dog(), new Cat()]

type AnimalKeys = typeof animals[number]['key'] // type 'cat' | 'dog'

Playground