Deeply union a type

deep_union.ts

export type DeepUnion<T, V> = T extends object
    ? { [P in keyof T]: DeepUnion<T[P], V> }
    : T | V;
  
// type Example1 = DeepUnion<["hello", [1, 2, 3]], null>;
//               = ["hello" | null, [1 | null, 2 | null, 3 | null]];
  
// type Example2: = DeepUnion<{ name: string, age: number }, undefined>;
//                = DeepUnion<{ name: string | undefined, age: number | undefined }, undefined>;

// type Example3 = DeepUnion<{ [name: string]: number }, string>;
//               = { [name: string]: number | string };