Type Alias KeyOfType<T, V>

KeyOfType: keyof {
[K in UnionKey<T> as Normalize<T>[K] extends V ? K : never]: void
}

Extracts keys from T whose value types extend V.

Type Parameters

T
The target type
V
The value type to match against

Example

type Result = KeyOfType<
	{ a: string; b: number; c: string },
	string
>;
//   ^?
// "a" | "c"

Example: Handles unions by using `Normalize`

type A = { a: string };
type B = { b: number };

type Result = KeyOfType<A | B, string | undefined>;
//   ^?
// "a"