node.js - Chaining Express.js 4's res.status(401) to a redirect

Question

I'd like to send a response code of 401 if the requesting user is not authenticated, but I'd also like to redirect when the request was an HTML request. I've been finding that Express 4 doesn't allow this:

res.status(401).redirect('/login')

Does anyone know of a way to handle this? This might not be a limitation of Express, since I'm asking to essentially pass two headers, but I don't see why that should be the case. I should be able to pass a "not authenticated" response and redirect the user all in one go.

Answer 1

There are some subtle diferences with the methods for sending back a new location header.

With redirect:

app.get('/foobar', function (req, res) {
  res.redirect(401, '/foo');
});
// Responds with
HTTP/1.1 401 Unauthorized
X-Powered-By: Express
Location: /foo
Vary: Accept
Content-Type: text/plain; charset=utf-8
Content-Length: 33
Date: Tue, 07 Apr 2015 01:25:17 GMT
Connection: keep-alive

Unauthorized. Redirecting to /foo

With status and location:

app.get('/foobar', function (req, res) {
  res.status(401).location('/foo').end();
});
// Responds with
HTTP/1.1 401 Unauthorized
X-Powered-By: Express
Location: /foo
Date: Tue, 07 Apr 2015 01:30:45 GMT
Connection: keep-alive
Transfer-Encoding: chunked

With the original (incorrect) approach using redirect:

app.get('/foobar', function (req, res) {
  res.status(401).redirect('/foo')();
});
// Responds with 
HTTP/1.1 302 Moved Temporarily
X-Powered-By: Express
Location: /foo
Vary: Accept
Content-Type: text/plain; charset=utf-8
Content-Length: 38
Date: Tue, 07 Apr 2015 01:26:38 GMT
Connection: keep-alive

Moved Temporarily. Redirecting to /foo

So it looks like redirect will abandon any previous status codes and send the default value (unless specified inside the method call). This makes sense due to the use of middleware within Express. If you had some global middleware doing pre-checks on all requests (like checking for the correct accepts headers, etc.) they wouldn't know to redirect a request. However the authentication middleware would and thus it would know to override any previous settings to set them correctly.

UPDATE: As stated in the comments below that even though Express can send a 4XX status code with a Location header does not mean it is an acceptable response for a request client to understand according to the specs. In fact most will ignore the Location header unless the status code is a 3XX value.