Chaining Express.js 4's res.status(401) to a redirect
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.
You can certainly send a Location: /login header alongside with your 401 page, however, this is ill-advised, and most browsers will not follow it, as per rfc2616.
One way to do overcome this, is to serve <meta http-equiv="refresh" content="0; url=/login"> alongside with your 401 page:
res.set('Content-Type', 'text/html');
res.status(401).send('<!DOCTYPE html><html><head><meta http-equiv="refresh" content="0; url=/login"></head></html>`);