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src/global/tools.ts

@@ -0,0 +1,21 @@
+export const groupBy = <T, K extends keyof any>(arr: T[], key: (i: T) => K) =>
+  arr.reduce((groups, item) => 
+  {
+    (groups[key(item)] ||= []).push(item);
+    return groups;
+  }, {} as Record<K, T[]>);
+
+export function groupByMap<K, V>(list: Array<V>, keyGetter: (input: V) => K): Map<K, Array<V>> 
+{
+    const map = new Map<K, Array<V>>();
+    list.forEach((item) => {
+         const key = keyGetter(item);
+         const collection = map.get(key);
+         if (!collection) {
+             map.set(key, [item]);
+         } else {
+             collection.push(item);
+         }
+    });
+    return map;
+}