Extract keys of T whose values match V
type Obj = { a: number; b: string; c: number; d: boolean };type NumKeys = KeysByValue<Obj, number>; // "a" | "c" Copy
type Obj = { a: number; b: string; c: number; d: boolean };type NumKeys = KeysByValue<Obj, number>; // "a" | "c"
Extract keys of T whose values match V