Typescript Utility Types

utility-types.d.ts

type OptionalTypeOrNull<T> = T | undefined | null;
type Nullish = undefined | null;
type Falsy = false | "" | 0 | 0n | Nullish;
type Truthy<T> = T extends Falsy ? never : T;
type AnyCollection = ArrayLike<unknown>;
type AnyObject = { [p: string]: AnyObject | AnyCollection | unknown };
type Maybe<T> = T | Nullish;
type MaybePromise<T> = Promise<T> | T;
type Immutable<T> = {
  readonly [K in keyof T]: Immutable<T[K]>;
};