try something

app.js

@@ -11,7 +11,7 @@ app.use('/html', express.static(path.join(__dirname, 'html')));
 
 // Serve the index.html file at the root URL
 app.get('/', (req, res) => {
-    res.sendFile(path.join(__dirname, 'index.html'));
+    res.sendFile(path.join(__dirname, 'index.js'));
 });
 
 // Serve the test.html file at /test URL