DeepPartial type - allow undefined / null instantiation of nested fields in a Typescript type (implemented before I found standard implementations + good practice :) ).

DeepPartial.ts

export type DeepPartial<T> = {
  [P in keyof T]?: NonNullable<T[P]> extends Array<infer U>
  ? Array<DeepPartial<NonNullable<U>>> | null
  : NonNullable<T[P]> extends ReadonlyArray<infer V>
  ? ReadonlyArray<DeepPartial<NonNullable<V>>> | null
  : NonNullable<T[P]> extends Date
  ? Date
  : NonNullable<T[P]> extends {}
  ? DeepPartial<NonNullable<T[P]>> | null
  : NonNullable<T[P]> | null;
};