Useful Typescript global types

TypeScript globals.md

global.d.ts

// Returns the optional keys of T as a union of string literals
declare type OptionalKeys<T> = Exclude<
  {
    [K in keyof T]: T extends Record<K, T[K]> ? never : K;
  }[keyof T],
  undefined
>;

// Makes all optional properties in T required
declare type OptionalParams<T> = Required<Pick<T, OptionalKeys<T>>>;

// Returns a Readonly type with all optional properties in T required
declare type OptionalDefaults<T> = Readonly<OptionalParams<T>>;

// Returns a Readonly type with all optional properties in T required excluding keys from K
declare type OptionalDefaultsPartial<T, K extends keyof T> = Omit<
  OptionalDefaults<T>,
  K
>;