www-redirect.js

// This is for SEO: We *only* want to serve from
// either www.domain.com or just domain.com but *not* both.
// So we need to choose and then do a 301 redirect to get
// traffic where we want it.
//
// NOTE: Don't hardcode the http:// or https:// in the redirect
// URI; this makes life suck when switching between dev and prod
// environments - use req.protocol instead as we do below.
//
// Also note that in order to use req.protocol reliably behind a
// proxy performing SSL termination (such as Elastic Load Balancer),
// you need to make sure that the trust proxy setting is enabled.
// This will ensure that req.protocol returns the protocol that
// the browser sees, not the protocol that finally made it to
// your server.
//
// Be sure to use req.headers.host instead of req.host, as the
// latter strips out the port number. So, if you were to handle
// a request for www.example.com:3000, you'd redirect the user
// to www.example.com, minus the correct port number.

// app.all('/*', function (req, res, next) {
//   if (req.headers.host.match(/^www\./) !== null ) {
//     // 301 is a "Moved Permanently" redirect.
//     res.redirect(301, req.protocol + '://' + req.headers.host.replace(/^www\./, '') + req.url);
//   } else {
//     next();
//   }
// });

function wwwRedirect (req, res, next) {
  if (req.headers.host.slice(0, 4) === 'www.') {
    var newHost = req.headers.host.slice(4);
    // 301 is a "Moved Permanently" redirect.
    return res.redirect(301, req.protocol + '://' + newHost + req.originalUrl);
  }
  next();
}

app.use(wwwRedirect);