use ES6 Map if we can (#602)

src/Common/ArrayHashMap.ts

@@ -1,49 +1,9 @@
-import { HashMap } from "./HashMap";
-
 /**
  * Hash map of arrays which allows to:
  * - push an item by key: add to array and create array if needed
  * - remove item by key: remove from array and delete array if needed
  */
-
-export class ArrayHashMap<T> {
-  private store: HashMap<T[]>;
-
-  constructor() {
-    this.store = new HashMap();
-  }
-
-  public has(key: string): boolean {
-    return this.store.has(key);
-  }
-
-  public get(key: string): T[] {
-    return this.store.get(key);
-  }
-
-  public size(): number {
-    return this.store.size();
-  }
-
-  public clear(): void {
-    this.store.clear();
-  }
-
-  public keys(): string[] {
-    return this.store.keys();
-  }
-
-  public delete(key: string): boolean {
-    return this.store.delete(key);
-  }
-
-  public forEach(key: string, iteratorFct: (value: T) => void) {
-    const values = this.store.get(key);
-    if (values) {
-      values.forEach((value) => iteratorFct(value));
-    }
-  }
-
+export class ArrayHashMap<T> extends Map<string, T[]> {
   /**
    * Insert item into array.
    * If no array, create one.
@@ -52,16 +12,8 @@ export class ArrayHashMap<T> {
    * @param item
    */
   public push(key: string, item: T): void {
-    let itemsArray: T[] = this.store.get(key);
-    if (!itemsArray) {
-      itemsArray = [item];
-      this.store.set(key, itemsArray);
-      return;
-    }
-
-    if (itemsArray.indexOf(item) === -1) {
-      itemsArray.push(item);
-    }
+    const array = this.get(key);
+    array ? array.includes(item) || array.push(item) : this.set(key, [item]);
   }
 
   /**
@@ -70,18 +22,11 @@ export class ArrayHashMap<T> {
    * @param key
    * @param itemToRemove
    */
-  public remove(key: string, itemToRemove: T) {
-    if (!this.store.has(key)) {
-      return;
-    }
-
-    const itemsArray = this.store.get(key);
-    const index = itemsArray.indexOf(itemToRemove);
-    if (index >= 0) {
-      itemsArray.splice(index, 1);
-      if (itemsArray.length === 0) {
-        this.store.delete(key);
-      }
+  public remove(key: string, itemToRemove: T): void {
+    const array = this.get(key);
+    if (array) {
+      const remaining = array.filter((item) => item !== itemToRemove);
+      remaining.length ? this.set(key, remaining) : this.delete(key);
     }
   }
 }