expressjs.com/2x/examples/session/app.js

/**
 * Module dependencies.
 */

var express = require('../../lib/express');

var app = express.createServer(
  express.logger(),

  // Required by session() middleware
  express.cookieParser(),

  // Populates:
  //   - req.session
  //   - req.sessionStore
  //   - req.sessionID (or req.session.id)
  express.session({ secret: 'keyboard cat' })
);

app.get('/', function(req, res){
  var body = '';
  if (req.session.views) {
    ++req.session.views;
  } else {
    req.session.views = 1;
    body += '<p>First time visiting? view this page in several browsers :)</p>';
  }
  res.send(body + '<p>viewed <strong>' + req.session.views + '</strong> times.</p>');
});

app.listen(3000);
console.log('Express app started on port 3000');