README.md

DeepNullable<Type> constructs a type by picking all properties from type Type recursively and include null property values for all of them

interface Company {
  name: string;
  employees: { name: string }[];
}

type DeepNullableCompany = DeepNullable<Company>;
//   ^? { name: string | null; employees: { name: string | null }[] }

Useful when object type is a source of truth and you need to have nullable object type, meaning property values can be null

TS Playground – https://tsplay.dev/mZ1roN