declare global {
  interface Array<T> {
    flatMap<U>(
      callbackfn: (value: T, index: number, array: T[]) => U[] | undefined,
      thisArg?: any
    ): U[];
  }
}

export function maybePush<T = any>(list: T[], item: T) {
  if (!list.includes(item)) {
    list.push(item);
  }
  return list;
}