CODEWITHSUNDEEP
javascripttypescript
Murat Karagöz
Murat Karagöz

Reputation: 37584

Typescript: Is it possible to reference type aliases

Typescript allows us to use string literals as types. The question is can I reference them with the dot-notation? For example I have a type like this

export type SomeTypes = 'OPEN' | 'CLOSED' | 'PROGRESSED' | 'DONE';

Can I somehow use it like this?

if(typecheck === SomeTypes.OPEN)

Right now I have to write out the string literal which is not entirely the type safety way. It looks like this

if(typecheck === 'OPEN')

Upvotes: 0

Views: 628

Answers (1)

Michael Rose
Michael Rose

Reputation: 7820

Have a look at TypeScript 2.4 - it supports String Enumerations.

Apart from that (since 2.4 introduces breaking changes) a more expressive "workaround" is as follows - define the constants as variables and then provide the alias upon the constants:

export const SOME_TYPE_OPEN = 'OPEN';
export const SOME_TYPE_CLOSED = 'CLOSED';
...
export type SomeType = SOME_TYPE_OPEN | SOME_TYPE_CLOSED | ...;

Then you can use:

function getIt(value: SomeType) {
    if (SOME_TYPE_OPEN === value) { ... }
    ...
}

Upvotes: 1

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