webpack/lib/util/SetHelpers.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

"use strict";

/**
 * intersect creates Set containing the intersection of elements between all sets
 * @param {Set[]} sets an array of sets being checked for shared elements
 * @returns {Set<TODO>} 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
 * @param {Set<TODO>} bigSet a Set which contains the original elements to compare against
 * @param {Set<TODO>} smallSet the set whos elements might be contained inside of bigSet
 * @returns {boolean} returns true if smallSet contains all elements inside of the bigSet
 */
const isSubset = (bigSet, smallSet) => {
	if (bigSet.size < smallSet.size) return false;
	for (const item of smallSet) {
		if (!bigSet.has(item)) return false;
	}
	return true;
};

exports.intersect = intersect;
exports.isSubset = isSubset;