ExpressJS Server – How to handle multiple domains

Vadim was almost onto the right idea. You can configure how to respond to each domain with the vhost middleware:

// `baz.com`
var app = express.createServer();
app.get( "https://stackoverflow.com/", routes.index );

// ...

express.createServer()
    .use( express.vhost( 'foo.com', express.static( '/var/www/foo' ) ) )
    .use( express.vhost( 'bar.net', express.static( '/var/www/bar' ) ) )
    .use( express.vhost( 'baz.com', app ) )
    .use( function( req, res ) {
        res.send('Sorry, I do not know how to handle that domain.');
    })
    .listen( ... );

routes.index can then be simplified to handle only baz.com requests:

exports.index = function( req, res ) {
    // ... lines ...
    res.render( 'index', { title: 'Baz Title example' } );
};

Edit

As for comparisons:

The switch would effectively be done first and would determine how to handle all requests based on the host — similar to:

express.createServer().use(function( req, res, next ) {
    switch( req.host ) {
        case 'foo.com': express.static( '/var/www/foo' )( req, res, next ); break;
        case 'bar.net': express.static( '/var/www/bar' )( req, res, next ); break;
        case 'baz.com': app.handle( req, res, next ); break;
        default: res.send( ... );
    }
}).listen( ... );

It allows you to set the stack on start so any middleware is available immediately:

server.stack = [
    express.vhost( 'foo.com', ... ),
    express.vhost( 'bar.net', ... ),
    express.vhost( 'baz.com', ... ),
    [Function]
];

These also reflect the 2 possible sources of issues you might have:

Same stack without filters

Each Application only has 1 middleware stack, which all of the middleware you’re using is being added directly to with app.use(...). Despite adding some under conditions, you’re still getting:

app.stack = [
    // ...,
    app.router,
    express.static( '/var/www/foo' ),
    express.static( '/var/www/bar' )
];

And the condition won’t change how the static middlewares respond — which is by req.path, not req.host — only when they’re in the stack to start responding.

State of the stack

And, if the static middlewares aren’t added until after another request has been made, then I take it they aren’t available immediately:

// GET http://foo.com/file 404
app.stack = [ app.router ]

// GET http://foo.com/ 200
app.stack = [ app.router, express.static( '/var/www/foo' ) ]

// GET http://foo.com/file 200
app.stack = [ app.router, express.static( '/var/www/foo' ) ]

This may also mean the same static middleware could be added to the stack multiple times:

// 3x GET http://foo.com/
app.stack = [
    app.router,
    express.static( '/var/www/foo' ),
    express.static( '/var/www/foo' ),
    express.static( '/var/www/foo' )
]

And having their addition depend on other requests also suggests a possible race conditions:

// was `foo.com` or `bar.net` first?
app.stack = [
    app.router,
    express.static( ? ),
    express.static( ? )
]