Added function to save and load a save game.

src/game/SaveGame.test.ts

@@ -0,0 +1,32 @@
+import "jest"
+import { saveGameKey, saveGame, loadGame } from './SaveGame';
+
+describe("SaveGame", () => {
+    const state = {
+        Level: 42,
+        Score: 89,
+    };
+
+    beforeEach(() => {
+        localStorage.clear();
+    });
+
+    test("save game", () => {
+        saveGame(state);
+        const inStore = localStorage.getItem(saveGameKey);
+        expect(inStore).not.toBeNull();
+        const loaded = JSON.parse(inStore as string);
+        expect(loaded).toEqual(state);
+    });
+
+    test("save game not exists", () => {
+        const loaded = loadGame();
+        expect(loaded).toBeNull();
+    });
+    
+    test("load game", () => {
+        saveGame(state);
+        const loaded = loadGame();
+        expect(loaded).toEqual(state);
+    });
+});

src/game/SaveGame.ts

@@ -0,0 +1,20 @@
+export const saveGameKey = "save_game";
+
+export interface SaveGame {
+    Level: number
+    Score: number
+}
+
+export function saveGame(saveGame: SaveGame) {
+    localStorage.setItem(saveGameKey, JSON.stringify(saveGame));
+}
+
+export function loadGame(): SaveGame | null {
+    const saveGame = localStorage.getItem(saveGameKey);
+
+    if(saveGame) {
+        return JSON.parse(saveGame);
+    }
+
+    return null;
+}