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keys-of-union.d.ts
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keys-of-union.d.ts
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/**
Create a union of all keys from a given type, even those exclusive to specific union members.
Unlike the native `keyof` keyword, which returns keys present in **all** union members, this type returns keys from **any** member.
@link https://stackoverflow.com/a/49402091
@example
```
import type {KeysOfUnion} from 'type-fest';
type A = {
common: string;
a: number;
};
type B = {
common: string;
b: string;
};
type C = {
common: string;
c: boolean;
};
type Union = A | B | C;
type CommonKeys = keyof Union;
//=> 'common'
type AllKeys = KeysOfUnion<Union>;
//=> 'common' | 'a' | 'b' | 'c'
```
@category Object
*/
export type KeysOfUnion<ObjectType> = ObjectType extends unknown
? keyof ObjectType
: never;