webpack/lib/util/SetHelpers.js

"use strict";

exports.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;
};

exports.isSubset = (bigSet, smallSet) => {
	if (bigSet.size < smallSet.size) return false;
	for (const item of smallSet) {
		if (!bigSet.has(item)) return false;
	}
	return true;
};