Typescript helpers for building interfaces

TypeScript Helpers.ts

/**
 * Make all properties partial and then pick only some that are required:
 * https://stackoverflow.com/questions/52703321/make-some-properties-optional-in-a-typescript-type
 */
export type OptionalExceptFor<T, TRequired extends keyof T> = Partial<T> & Pick<T, TRequired>

/**
 * Type XOR
 */
type Diff<T, U> = T extends U ? never : T;

/**
 * Make all properties required except certain fields.
 */
export type RequiredExceptFor<T, TOptional extends keyof T> = Pick<T, Diff<keyof T, TOptional>> & Partial<T>;

/**
 * Optional makes all object fields optional
 */
export type Optional<T, K extends keyof T> = Pick<Partial<T>, K> & Omit<T, K>;

/**
 * Deep Partial makes all object fields optional recursively
 */
export type DeepPartial<T> = {
  [P in keyof T]?: DeepPartial<T[P]>;
};