Function intersect

lib/util/SetHelpers.js:14–37

(sets)

 * @returns {Set<T>} returns a new Set containing the intersecting items
 */
const intersect = (sets) => {
	if (sets.length === 0) return new Set();
	if (sets.length === 1) return new Set(sets[0]);
	let minSize = Infinity;
	let minIndex = -1;
	for (let i = 0; i < sets.length; i++) {
		const size = sets[i].size;
		if (size < minSize) {
			minIndex = i;
			minSize = size;
		}
	}
	const current = new Set(sets[minIndex]);
	for (let i = 0; i < sets.length; i++) {
		if (i === minIndex) continue;
		const set = sets[i];
		for (const item of current) {
			if (!set.has(item)) {
				current.delete(item);
			}
		}
	}
	return current;
};

/**
 * Checks if a set is the subset of another set