starting SymptomVsSymptomChartDataProviderTest

docs/SymptomsCausedByCOVIDLots/js/Sets.js

@@ -0,0 +1,20 @@
+class Sets {
+
+    static filterSet(set, predicate) {
+        return new Set([...set].filter(predicate));
+    }
+
+    static union(sets) {
+        return sets.reduce(
+            (union, set) => new Set([...union, ...set]),
+            new Set());
+    }
+
+    static intersection(set1, set2) {
+        return new Set([...set1].filter(x => set2.has(x)));
+    }
+
+    static isEmpty(set) {
+        return set.size == 0;
+    }
+}