How to programmatically send a 404 response with Express/Node?

Question

I want to simulate a 404 error on my Express/Node server. How can I do that?

Malamute

How would "simulated" differ from a "real" one? – Metacenter

Answer 1

Since Express 4.0, there's a dedicated sendStatus function:

res.sendStatus(404);

---

If you're using an earlier version of Express, use the status function instead.

res.status(404).send('Not found');

Kierkegaardian

This also works with rendered pages: res.status(404).render('error404') – Mecham

Worth noting that on it's own res.status(404); wont send a response AFAIK. It needs to either be chained with something, e.g. res.status(404).end(); or your second example, or it needs to be followed by e.g. res.end();, res.send('Not found'); – Onus

@UpTheCreek, I'll remove the first example from the code to avoid the potential for that confusion. – Kierkegaardian

shorter version res.sendStatus(404) – Betty

@Betty plan and simple. – Absinthism

Answer 2

Updated Answer for Express 4.x

Rather than using res.send(404) as in old versions of Express, the new method is:

res.sendStatus(404);

Express will send a very basic 404 response with "Not Found" text:

HTTP/1.1 404 Not Found
X-Powered-By: Express
Vary: Origin
Content-Type: text/plain; charset=utf-8
Content-Length: 9
ETag: W/"9-nR6tc+Z4+i9RpwqTOwvwFw"
Date: Fri, 23 Oct 2015 20:08:19 GMT
Connection: keep-alive

Not Found

Avaavadavat

I'm pretty sure it's just res.status(404) not res.sendStatus(404). – Trotskyism

res.sendStatus(404) is correct. It is equivalent to res.status(404).send() – Goins

Yep res.sendStatus(404); is equivalent to res.status(404).send('Not Found') – Apennines

@JakeWilson now what is it ?? – Niobe

Answer 3

You don't have to simulate it. The second argument to res.send I believe is the status code. Just pass 404 to that argument.

Let me clarify that: Per the documentation on expressjs.org it seems as though any number passed to res.send() will be interpreted as the status code. So technically you could get away with:

res.send(404);

Edit: My bad, I meant res instead of req. It should be called on the response

Edit: As of Express 4, the send(status) method has been deprecated. If you're using Express 4 or later, use: res.sendStatus(404) instead. (Thanks @badcc for the tip in the comments)

Typography

You could also send a message with the 404: res.send(404, "Could not find ID "+id) – Ansela

Sending a status code directly is deprecated in 4.x and will probably be removed at some point. Best to stick with .status(404).send('Not found') – Highchair

For Express 4: "express deprecated res.send(status): Use res.sendStatus(status) instead" – Supination

Answer 4

According to the site I'll post below, it's all how you set up your server. One example they show is this:

var http = require("http");
var url = require("url");

function start(route, handle) {
  function onRequest(request, response) {
    var pathname = url.parse(request.url).pathname;
    console.log("Request for " + pathname + " received.");

    route(handle, pathname, response);
  }

  http.createServer(onRequest).listen(8888);
  console.log("Server has started.");
}

exports.start = start;

and their route function:

function route(handle, pathname, response) {
  console.log("About to route a request for " + pathname);
  if (typeof handle[pathname] === 'function') {
    handle[pathname](response);
  } else {
    console.log("No request handler found for " + pathname);
    response.writeHead(404, {"Content-Type": "text/plain"});
    response.write("404 Not found");
    response.end();
  }
}

exports.route = route;

This is one way. http://www.nodebeginner.org/

From another site, they create a page and then load it. This might be more of what you're looking for.

fs.readFile('www/404.html', function(error2, data) {
            response.writeHead(404, {'content-type': 'text/html'});
            response.end(data);
        });

http://blog.poweredbyalt.net/?p=81

Cinder

Answer 5

From the Express site, define a NotFound exception and throw it whenever you want to have a 404 page OR redirect to /404 in the below case:

function NotFound(msg){
  this.name = 'NotFound';
  Error.call(this, msg);
  Error.captureStackTrace(this, arguments.callee);
}

NotFound.prototype.__proto__ = Error.prototype;

app.get('/404', function(req, res){
  throw new NotFound;
});

app.get('/500', function(req, res){
  throw new Error('keyboard cat!');
});

Valida

This example code is no longer at the link you reference. Might this apply to an earlier version of express? – Kierkegaardian

It actually stil applies to the existing code, all you have to do is to use the error handle middleware to catch the error. Ex: app.use(function(err, res, res, next) { if (err.message.indexOf('NotFound') !== -1) { res.status(400).send('Not found dude'); }; /* else .. etc */ }); – Valida

Answer 6

IMO the nicest way is to use the next() function:

router.get('/', function(req, res, next) {
    var err = new Error('Not found');
    err.status = 404;
    return next(err);
}

Then the error is handled by your error handler and you can style the error nicely using HTML.

Helvetia

Yeah, I agree, in a node/express context using the middleware is far more consistent. – Middle