starting SymptomVsSymptomChartDataProviderTest

docs/SymptomsCausedByCOVIDLots/js/SymptomVsSymptomChartDataProvider.js

@@ -0,0 +1,28 @@
+class SymptomVsSymptomChartDataProvider {
+
+    static retainCommonLots({ prrByLotX, prrByLotY }) {
+        const commonLots = SymptomVsSymptomChartDataProvider.#getCommonKeys(prrByLotX, prrByLotY);
+        return {
+            prrByLotX: SymptomVsSymptomChartDataProvider.#retainKeysOfDict(prrByLotX, commonLots),
+            prrByLotY: SymptomVsSymptomChartDataProvider.#retainKeysOfDict(prrByLotY, commonLots)
+        };
+    }
+
+    static #getCommonKeys(dict1, dict2) {
+        return Sets.intersection(
+            SymptomVsSymptomChartDataProvider.#getKeySet(dict1),
+            SymptomVsSymptomChartDataProvider.#getKeySet(dict2));
+    }
+
+    static #getKeySet(dict) {
+        return new Set(Object.keys(dict));
+    }
+
+    static #retainKeysOfDict(dict, keys2Retain) {
+        const entries2Retain =
+            Object
+                .entries(dict)
+                .filter(([key, _]) => keys2Retain.has(key));
+        return Object.fromEntries(entries2Retain);
+    }
+}