Use an object indexes to define a possible types in typescript

Question

I know that we can extract type possibilies using an array:

const fruits = ['Apple', 'Pear', 'Banana'] as const
type fruitType = typeof fruits[number] // "Apple" | "Pear" | "Banana"

I wonder if we can do this using object indexes instead?

const fruits = {
  apple: { shape: 'round', color: 'red' },
  pear: { shape: 'pear-like', color: 'yellow' },
  banana: { shape: 'banana-shaped', color: 'banana-colored' }
}
type fruitType = typeof indexes of fruits // "apple" | "pear" | "banana"

Thanks!

Those are generally termed "keys", not "indexes", when applied to objects. Thus the keyword in TypeScript keyof... — Heretic Monkey
– Heretic Monkey, Commented Oct 19, 2021 at 19:33
It looks very strange. Usually the union type is used fro those puposes - type fruitTypes = 'Apple' | 'Pear' | 'Banana'. Then that type is implemented for both const fruits: fruitTypes and const fruits: { [key: fruitTypes]: unknown }; — Gorynych
– Gorynych, Commented Oct 19, 2021 at 19:40

bloo · Accepted Answer · 2021-10-20 01:23:45Z

2

I believe this is what you are looking for:

type fruitType = keyof typeof fruits // "apple" | "pear" | "banana";

Here is a link to the documentation as @jcalz suggested, and the Playground

edited Oct 20, 2021 at 1:23

answered Oct 19, 2021 at 19:50

bloo

1,5602 gold badges14 silver badges21 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

jcalz Over a year ago

Consider linking to the handbook documentation for the keyof type operator

Collectives™ on Stack Overflow

Use an object indexes to define a possible types in typescript

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related