more useful TS types

global.d.ts

declare global {
  type NonFalsy<T> = T extends false | 0 | "" | null | undefined | 0n ? never : T

  interface Array<T> {
    filter(predicate: BooleanConstructor, thisArg?: any): NonFalsy<T>[]
    includes<S, R extends `${Extract<S, string>}`>(
      this: ReadonlyArray<R>,
      searchElement: S,
      fromIndex?: number,
    ): searchElement is R & S
  }

  interface ReadonlyArray<T> {
    filter(predicate: BooleanConstructor, thisArg?: any): NonFalsy<T>[]
    includes<S, R extends `${Extract<S, string>}`>(
      this: ReadonlyArray<R>,
      searchElement: S,
      fromIndex?: number,
    ): searchElement is R & S
  }
}