Interface keys from array in TypeScript

Question

Is there a way to enforce the keys of an interface to be used from an array of strings:

E.g. If we have the following array:

const myArray = ['key1', 'key2'];

I would like to create a new interface called MyInterface that would force all myArray entries to be the keys of an object:

const myObj: MyInterface = {
  'key1': true,
  'key2': false,
}

emeraldsanto · Accepted Answer · 2022-05-13 23:45:50Z

6

You can use the keyof operator for exactly this purpose.

interface MyInterface {
  key1: boolean;
  key2: boolean;
}

const myObj: MyInterface = {
  key1: true,
  key2: false,
}

const myArray: Array<keyof MyInterface> = ['key1', 'key2'];
// or ...
const myOtherArray: Array<keyof typeof myObj> = ['key1', 'key2'];

You could also go backwards like so

const myArray = ['key1', 'key2'] as const;

type MyType = Record<typeof myArray[number], boolean>;

const myObj: MyType = {
  key1: true,
  key2: false,
}

answered May 13, 2022 at 23:45

emeraldsanto

4,7611 gold badge17 silver badges28 bronze badges

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

4 Comments

Ovidijus Parsiunas Over a year ago

Thanks for the reply. What is the [number] syntax in TypeScript?

emeraldsanto Over a year ago

You can learn more about this here @OvidijusParsiunas typescriptlang.org/docs/handbook/2/indexed-access-types.html

dwu39 Over a year ago

@emeraldsanto is there a way to have mixed value types? Some values are booleans, strings, etc

dwu39 Over a year ago

You can use "ReadonlyArray<keyof MyInterface>" if you need myArray as a const

Collectives™ on Stack Overflow

Interface keys from array in TypeScript

1 Answer 1

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related