Invalid movements are now displayed correctly

src/main.ts

@@ -19,6 +19,7 @@ class HttpServer {
   public onStart(): void {
     let chessboard: Chessboard = createInitialChessboard();
     let app: express.Application = express();
+    
     app.use(bodyParser.json());
     app.use(bodyParser.urlencoded({ extended: true }));
     app.use(express.static(PUBLIC_DIR));
@@ -29,7 +30,7 @@ class HttpServer {
     });
 
     app.get('/',  (req: express.Request, res: express.Response) => {
-      res.render('index', {error: "Erreur"});
+      res.render('index', {error: null});
     })
 
     app.get("/status.js", (req: express.Request, res: express.Response) => {
@@ -38,9 +39,9 @@ class HttpServer {
 
     app.post("/", (req: express.Request, res: express.Response) => {
       let unparsedMove: string = req.body.move;
-      chessboard = processMove(chessboard, unparsedMove);
-      //res.redirect("/");
-      res.render('index', {error: null});
+      let didPerfom: boolean = processMove(chessboard, unparsedMove);
+      let message: string = didPerfom ? "" : "Invalid movement!"
+      res.render('index', {error: message});
     });
   }
 }