diff --git a/lib/www/server/lib/utils/setops.js b/lib/www/server/lib/utils/setops.js
new file mode 100644
index 0000000..3ddf8f3
--- /dev/null
+++ b/lib/www/server/lib/utils/setops.js
@@ -0,0 +1,52 @@
+
+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
+}