How do I add possible values to existing union type declared in standard library in TypeScript?

Question

Consider this PermissionName type declared in lib.dom.d.ts:

type PermissionName = "geolocation" | "notifications" | // More...

Can I somehow add a value to it from my own app.d.ts file? For example (code doesn't work):

declare global {

    type PermissionName = PermissionName | "local-fonts";

}

export {}

so that this code would work (this is the reason why I cannot declare new type, because other APIs is using this type)?

await navigator.permissions.query({
    name: "local-fonts"
});

Current workaround:

await navigator.permissions.query({
    name: <any>"local-fonts"
});

Does this answer your question? [Extend globally declared Type in Typescript](https://stackoverflow.com/questions/59968957/extend-globally-declared-type-in-typescript) — Tanek Loc, Dec 10 '22 at 09:59
@TanekLoc hi, I have seen that one before. Yeah it's a duplicate though I am trying to get a newer answer in hope that there is better solution. — Luke Vo, Dec 10 '22 at 12:10

score 2 · Accepted Answer · answered Dec 10 '22 at 15:07

2

What you need to augment is not PermissionName, but navigator.permissions.query

Playground

declare global {
  interface Permissions {
    query(permissionDesc: { name: 'local-fonts' }): Promise<PermissionStatus>;
  }
}
navigator.permissions.query({
  name: "local-fonts"
});

export { }

answered Dec 10 '22 at 15:07

Dimava

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Ah that's very clever! I guess this is a good solution in this case although sometimes many APIs may use the same time then we have to augment that many APIs. – Luke Vo Dec 10 '22 at 15:20

How do I add possible values to existing union type declared in standard library in TypeScript?

1 Answers1