dougal-software/lib/www/server/lib/utils/setops.js

function unique(arr) {
	const set = new Set(arr.map(JSON.stringify));
	return Array.from(set).map(JSON.parse);
}

function duplicates(arr) {
	const seen = new Set();
	const dups = new Set();
	for (const item of arr.map(JSON.stringify)) {
		if (seen.has(item)) {
			dups.add(item);
		} else {
			seen.add(item);
		}
	}
	return Array.from(dups).map(JSON.parse);
}

function union(arr1, arr2) {
	const set = new Set([...arr1, ...arr2].map(JSON.stringify));
	return Array.from(set).map(JSON.parse);
}


function intersection(arr1, arr2) {
	const set2 = new Set(arr2.map(JSON.stringify));
	return arr1.filter(item => set2.has(JSON.stringify(item)));
}

function difference(arr1, arr2) {
	const set2 = new Set(arr2.map(JSON.stringify));
	return arr1.filter(item => !set2.has(JSON.stringify(item)));
}

function symmetricDifference(arr1, arr2) {
	const set1 = new Set(arr1.map(JSON.stringify));
	const set2 = new Set(arr2.map(JSON.stringify));
	return [
		...arr1.filter(item => !set2.has(JSON.stringify(item))),
		...arr2.filter(item => !set1.has(JSON.stringify(item)))
	];
}

module.exports = {
	unique,
	duplicates,
	union,
	intersection,
	difference,
	symmetricDifference
}