How to redirect 404 errors to a page in ExpressJS?

Question

I found this example quite helpful:

https://github.com/visionmedia/express/blob/master/examples/error-pages/index.js

So, it is actually this part:

// "app.router" positions our routes
// above the middleware defined below,
// this means that Express will attempt
// to match & call routes _before_ continuing
// on, at which point we assume it's a 404 because
// no route has handled the request.

app.use(app.router);

// Since this is the last non-error-handling
// middleware use()d, we assume 404, as nothing else
// responded.

// $ curl http://localhost:3000/notfound
// $ curl http://localhost:3000/notfound -H "Accept: application/json"
// $ curl http://localhost:3000/notfound -H "Accept: text/plain"

app.use(function(req, res, next) {
  res.status(404);

  // respond with html page
  if (req.accepts('html')) {
    res.render('404', { url: req.url });
    return;
  }

  // respond with json
  if (req.accepts('json')) {
    res.json({ error: 'Not found' });
    return;
  }

  // default to plain-text. send()
  res.type('txt').send('Not found');
});

I think you should first define all your routes and as the last route add

//The 404 Route (ALWAYS Keep this as the last route)
app.get('*', function(req, res){
  res.status(404).send('what???');
});

An example app which does work:

app.js:

var express = require('express'),
    app = express.createServer();

app.use(express.static(__dirname + '/public'));

app.get('/', function(req, res){
  res.send('hello world');
});

//The 404 Route (ALWAYS Keep this as the last route)
app.get('*', function(req, res){
  res.send('what???', 404);
});

app.listen(3000, '127.0.0.1');

---

alfred@alfred-laptop:~/node/stackoverflow/6528876$ mkdir public
alfred@alfred-laptop:~/node/stackoverflow/6528876$ find .
alfred@alfred-laptop:~/node/stackoverflow/6528876$ echo "I don't find a function for that... Anyone knows?" > public/README.txt
alfred@alfred-laptop:~/node/stackoverflow/6528876$ cat public/README.txt 

.
./app.js
./public
./public/README.txt

alfred@alfred-laptop:~/node/stackoverflow/6528876$ curl http://localhost:3000/
hello world
alfred@alfred-laptop:~/node/stackoverflow/6528876$ curl http://localhost:3000/README.txt
I don't find a function for that... Anyone knows?

You can put a middleware at the last position that throws a NotFound error,
or even renders the 404 page directly:

app.use(function(req,res){
    res.status(404).render('404.jade');
});

The above answers are good, but in half of these you won't be getting 404 as your HTTP status code returned and in other half, you won't be able to have a custom template render. The best way to have a custom error page (404's) in Expressjs is

app.use(function(req, res, next){
    res.status(404).render('404_error_template', {title: "Sorry, page not found"});
});

Place this code at the end of all your URL mappings.

At the last line of app.js just put this function. This will override the default page-not-found error page:

app.use(function (req, res) {
    res.status(404).render('error');
});

It will override all the requests that don't have a valid handler and render your own error page.

The answer to your question is:

app.use(function(req, res) {
    res.status(404).end('error');
});

And there is a great article about why it is the best way here.