CORS with Authentication

When dealing with authentication (e.g., cookies or JWT), you need to ensure CORS configuration allows credentials:

const corsOptions = {
  origin: 'http://example.com',
  methods: 'GET,POST',
  allowedHeaders: 'Content-Type,Authorization',
  credentials: true, // Allow credentials (cookies, headers)
};

app.use(cors(corsOptions));

Make sure that the client-side code also includes credentials in requests:

fetch('http://api.example.com/data', {
  method: 'GET',
  credentials: 'include' // Include cookies in the request
});