# Responding to Requests

Any action may terminate a request one of three ways:

1. Throw an error - An error handler is invoked.
2. Return a value - A renderer is invoked.
3. Finalize the response

Finalizing a response is for cases where you need the most control. It allows you to terminate the response any way you need without invoking a renderer.

const loggedIn = createAction(({ req, res }) => {
    // must be authenticated!

    if (!req.headers.authorization) {
        // cause redirect
        res.statusCode = 302;
        res.setHeader('Location', '/login');

        // finalize response to ignore remaining actions
        res.end();
    }
});

const setJson = createAction(({ res }) => {
    res.setHeader('Content-Type', 'application/json');
});

createRoute({
    method: 'GET',
    url: '/api/users',
    actions: [loggedIn, setJson, () => {
        // return a value to invoke a renderer
        return {
            users: [{ name: 'April' }, { name: 'Leo' }]
        };
    }],
});

In this example if the client did not provide an 'authorization' header, the loggedIn action will finalize the response. This terminates the request and skips all remaining actions.

Otherwise the setJson action sets the 'Content-Type' of the response to 'application/json'.

The last remaining action returns a value. This invokes a renderer best matching the 'Content-Type' header, in this example a renderer matching 'application/json' will be used.

The appropriate renderer will finalize a response to the client. If an error was thrown then an error handler best matching the 'Content-Type' header would intercept the response.