Add a method for checking whether there is a winner

src/js/Game.js

@@ -8,6 +8,11 @@ import { State } from "./State.js";
  */
 export class Game
 {
+    /**
+     * The number of chips required for a win.
+     */
+    static #count = 4;
+
     /**
      * The width of the board.
      */
@@ -74,6 +79,50 @@ export class Game
         return this.state.board;
     }
 
+    /**
+     * Gets the id of the player that is winning.
+     *
+     * @type {CellOwner}
+     */
+    get winner()
+    {
+        for (let yOffset = 0; yOffset <= 1; yOffset++)
+        {
+            for (let xOffset = (yOffset === 1) ? -1 : 1; xOffset <= 1; xOffset++)
+            {
+                let lowerBound = Math.max(0, xOffset * (Game.#count - 1) * -1);
+                let upperBound = Math.min(Game.#width, Game.#width - (xOffset * (Game.#count - 1)));
+
+                for (let y = 0; y < (Game.#height - yOffset * (Game.#count - 1)); y++)
+                {
+                    for (let x = lowerBound; x < upperBound; x++)
+                    {
+                        /**
+                         * @type {CellOwner[]}
+                         */
+                        let tokens = [];
+
+                        for (let i = 0; i < Game.#count; i++)
+                        {
+                            tokens.push(this.board[y + i * yOffset][x + i * xOffset]);
+                        }
+
+                        let player = tokens[0];
+
+                        if (
+                            player !== "" &&
+                            tokens.every((token) => token === player))
+                        {
+                            return player;
+                        }
+                    }
+                }
+            }
+        }
+
+        return null;
+    }
+
     /**
      * Dumps the state of the game.
      *