fix: build

packages/collection-utils/src/group-by.ts

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2022 StApps
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/**
+ * Group an array by a function
+ */
+export function groupBy<T>(collection: T[], group: (item: T) => string | undefined): Record<string, T[]> {
+  return collection.reduce((accumulator: Record<string, T[]>, item) => {
+    const key = group(item) ?? '';
+    accumulator[key] = accumulator[key] ?? [];
+    accumulator[key].push(item);
+    return accumulator;
+  }, {});
+}
+
+/**
+ * Group an array by a function (returns a Map, whose keys keep order info of items entry)
+ */
+export function groupByStable<T>(collection: T[], group: (item: T) => string | undefined): Map<string, T[]> {
+  return collection.reduce((accumulator: Map<string, T[]>, item) => {
+    const key = group(item) ?? '';
+    accumulator.set(key, accumulator.get(key) ?? []);
+    accumulator.get(key)?.push(item);
+    return accumulator;
+  }, new Map<string, T[]>());
+}
+
+/**
+ *
+ */
+export function groupByProperty<T extends object>(collection: T[], property: keyof T): Record<string, T[]> {
+  return groupBy(collection, item => item[property] as unknown as string);
+}