Refactor: use union type in ItemName type to implement Item interface

TypeScript/app/gilded-rose.ts

@@ -1,19 +1,22 @@
-import { AgedBrie, Passes, Surfras } from "./itemClasses";
-type ItemClasses = AgedBrie[] | Surfras[] | Passes[];
+import { Item } from "./itemClasses";
+
+interface ItemForSale extends Item {
+  handleQuality: () => void;
+  handleSellIn: () => void;
+}
 
 export class GildedRose {
-  items: ItemClasses;
-  constructor(items = [] as ItemClasses) {
+  items: ItemForSale[];
+  constructor(items = [] as ItemForSale[]) {
     this.items = items;
   }
 
   updateQuality() {
-    const updatedItems = this.items.map((item) => {
+    return this.items.map((item) => {
       item.handleSellIn();
       item.handleQuality();
 
       return item;
     });
-    return updatedItems as ItemClasses;
   }
 }

TypeScript/app/itemClasses.ts

@@ -1,9 +1,15 @@
-export class Item {
-  name: string;
-  sellIn: number;
-  quality: number;
+export type ItemName =
+  | "Aged Brie"
+  | "Backstage passes to a TAFKAL80ETC concert"
+  | "Conjured Mana Cake"
+  | "Sulfuras, Hand of Ragnaros";
 
-  constructor(name, sellIn, quality) {
+export class Item {
+  name;
+  sellIn;
+  quality;
+
+  constructor(name: ItemName, sellIn: number, quality: number) {
     this.name = name;
     this.sellIn = sellIn;
     this.quality = quality;