Bouncing a user back to their last place after authentication with Express 3

stack-auth-bounce.js

// Bouncing a user back to their last place after authentication with Express 3
// To accompany http://stackoverflow.com/a/12443844/1380669
// by therealplato 

var express = require('express');
var app = express();
require('http').createServer(app).listen(3000
, function(err){
  console.log(err || "Listening on 3000");
});

app.use(express.cookieParser());
app.use(express.session({secret:'apapppxxllerjam,dfa654163210321'}));
app.use(express.bodyParser());
app.use(express.logger('dev'));
app.use(app.router);

// If a user visits an auth page and we don't have .bounceTo in session,
// set it to: query['bounce']  ||  req.header('Referer')  ||  '/'
app.get('/auth/*', function(req, res, next){
  if(!!req.session.bounceTo){ // already have a bounce destination
    return next();
  } else {
    if(req.query['bounce']){
      req.session.bounceTo = req.query['bounce'];
    } else {  // no explicit destination, use referer or homepage
      req.session.bounceTo=req.header('Referer') || '/';  
    }
    return next();
  };
});

// continue to render a template or whatever. see bottom
// app.get('/auth/register', function(req, res, next){ ... });

// the register page posts a form:
app.post('/auth/register/form', function(req, res, next){
  // you do stuff and either succeed or fail:
  function createUser(req, callback){
    if(req.body.name.match(/^[a-zA-Z0-9]+$/)){ // e.g. valid user
      callback(null, {name: req.body.name});
    } else {
      callback({message:"Bad character"});
    };
  };

  createUser(req, function(err, user){
    if(err){  return res.redirect('/auth/failure')  };
    // save the user to session or something
    // with Express, it's `req.logIn(user);` to place user in req.user
    res.redirect('/auth/success');
  });

});

// Redirect appropriately
app.get('/auth/success', function(req, res){
  var tmp = req.session.bounceTo;
  delete req.session.bounceTo;
  res.redirect(tmp);
});

app.get('/auth/failure', function(req, res){
  res.redirect('/auth/register');
});
// Your login form can similarly redirect to /auth/success or /auth/failure

// example app routes:
app.get('/auth/register', function(req, res){ 
  res.send(200, 
  '<h1>/auth/register</h1>'
  +'<form action="/auth/register/form" method="post">'
  +'<p>Alphanumeric username only</p>'
  +'<input type="text" name="name" />'
  +'<input type="submit" value="Register!"/>'
  +'</form>');
});

app.get('/', function(req, res){ 
  res.send(200, 
  '<h1>/</h1>'
  +'<a href="/auth/register">/auth/register</a>'
  +'<a href="/test1">/test1</a>'
  +'<a href="/test2">/test2</a>'
  +'<a href="/test3">/test3</a>'
  ) 
});
app.get('/test1', function(req, res){ res.send(200, '<h1>/test1</h1><a href="/auth/register">/auth/register</a>') });
app.get('/test2', function(req, res){ res.send(200, '<h1>/test2</h1><a href="/auth/register?bounce=/test3">/auth/register?bounce=/test3</a>') });
app.get('/test3', function(req, res){ res.send(200, '<h1>/test3</h1><a href="/auth/register">/auth/register</a>') });