Example of a generic type alias that transforms a given type into a nullable type (including sub-properties in case of objects)

deep_nullable.ts

/**
 * Type alias to recursively make all properties of an object optionally undefined or null.
 * Adds | undefined | null to all objects and its properties.
 */
type DeepNullable<T> = T extends object
  ? { [k in keyof T]?: DeepNullable<T[k] | null> }
  : T | null;

interface TestObj {
  nothing: boolean;
  is: number;
  nullish: string;
  not: {
    even: {
      objects: boolean;
    };
    right: string;
  };
}

const testObj: TestObj = {
  nothing: true,
  is: 1,
  nullish: "yeah",
  not: {
    even: {
      objects: true
    },
    right: "yeah"
  }
};

const testNullable: DeepNullable<TestObj> = {};

Extra contraction:

type NulledT<T> = T | Null;

type DeepNullable<T> = T extends object
  ? { [k in keyof T]?: DeepNullable<NulledT<T[k]>> }
  : NulledT<T>;

Not more readable, just more concise