declare global {
	interface Set<T> {
		/** @summary check if any of the elements of `arr2` are included in `this` */
		anyOf(arr2: Array<T>): boolean;
		/** @summary return set items as array */
		arr(): Array<T>;
	}
}

Set.prototype.arr = function() {
	return Array.from(this);
}

Set.prototype.anyOf = function(arr2) {
	return !!this.arr().filter(e => arr2.includes(e)).length;
};