Modified by myself to use the newer, better, faster, stronger keygrip + cookies middleware. New usage is as simple as:

var express = require('express')
  , keygrip = require('keygrip')
  , cookies = require('cookies')
  , expressSession = require('express-session');
var app = express();
var keys = keygrip(["s3cr3tk3y1", "s3cr3tk3y2"]);
app.use(cookies.express(keys));
app.use(expressSession());

The original documentation is below, slightly modified to remove references to the old secret option, which is no longer required

var express = require('express')
var session = require('express-session')

var app = express()

app.use(session())

Setup session store with the given options.

Session data is not saved in the cookie itself, just the session ID.

• name - cookie name (formerly known as key). (default: 'connect.sid')
• store - session store instance.
• secret - session cookie is signed with this secret to prevent tampering.
• cookie - session cookie settings.
  • (default: { path: '/', httpOnly: true, secure: false, maxAge: null })
• genid - function to call to generate a new session ID. (default: uses uid2 library)
• rolling - forces a cookie set on every response. This resets the expiration date. (default: false)
• resave - forces session to be saved even when unmodified. (default: true)
• proxy - trust the reverse proxy when setting secure cookies (via "x-forwarded-proto" header). When set to true, the "x-forwarded-proto" header will be used. When set to false, all headers are ignored. When left unset, will use the "trust proxy" setting from express. (default: undefined)
• saveUninitialized - forces a session that is "uninitialized" to be saved to the store. A session is uninitialized when it is new but not modified. This is useful for implementing login sessions, reducing server storage usage, or complying with laws that require permission before setting a cookie. (default: true)
• unset - controls result of unsetting req.session (through delete, setting to null, etc.). This can be "keep" to keep the session in the store but ignore modifications or "destroy" to destroy the stored session. (default: 'keep')

Generate a custom session ID for new sessions. Provide a function that returns a string that will be used as a session ID. The function is given req as the first argument if you want to use some value attached to req when generating the ID.

NOTE be careful you generate unique IDs so your sessions do not conflict.

app.use(session({
  genid: function(req) {
    return genuuid(); // use UUIDs for session IDs
  }
}))

Please note that secure: true is a recommended option. However, it requires an https-enabled website, i.e., HTTPS is necessary for secure cookies. If secure is set, and you access your site over HTTP, the cookie will not be set. If you have your node.js behind a proxy and are using secure: true, you need to set "trust proxy" in express:

var app = express()
app.set('trust proxy', 1) // trust first proxy
app.use(session({cookie: { secure: true }
}))

For using secure cookies in production, but allowing for testing in development, the following is an example of enabling this setup based on NODE_ENV in express:

var app = express()
var sess = { cookie: {}
}

if (app.get('env') === 'production') {
  app.set('trust proxy', 1) // trust first proxy
  sess.cookie.secure = true // serve secure cookies
}

app.use(session(sess))

By default cookie.maxAge is null, meaning no "expires" parameter is set so the cookie becomes a browser-session cookie. When the user closes the browser the cookie (and session) will be removed.

To store or access session data, simply use the request property req.session, which is (generally) serialized as JSON by the store, so nested objects are typically fine. For example below is a user-specific view counter:

app.use(session(cookie: { maxAge: 60000 }}))

app.use(function(req, res, next) {
  var sess = req.session
  if (sess.views) {
    sess.views++
    res.setHeader('Content-Type', 'text/html')
    res.write('<p>views: ' + sess.views + '</p>')
    res.write('<p>expires in: ' + (sess.cookie.maxAge / 1000) + 's</p>')
    res.end()
  } else {
    sess.views = 1
    res.end('welcome to the session demo. refresh!')
  }
})

To regenerate the session simply invoke the method, once complete a new SID and Session instance will be initialized at req.session.

req.session.regenerate(function(err) {
  // will have a new session here
})

Destroys the session, removing req.session, will be re-generated next request.

req.session.destroy(function(err) {
  // cannot access session here
})

Reloads the session data.

req.session.reload(function(err) {
  // session updated
})

req.session.save(function(err) {
  // session saved
})

Updates the .maxAge property. Typically this is not necessary to call, as the session middleware does this for you.

Each session has a unique cookie object accompany it. This allows you to alter the session cookie per visitor. For example we can set req.session.cookie.expires to false to enable the cookie to remain for only the duration of the user-agent.

Alternatively req.session.cookie.maxAge will return the time remaining in milliseconds, which we may also re-assign a new value to adjust the .expires property appropriately. The following are essentially equivalent

var hour = 3600000
req.session.cookie.expires = new Date(Date.now() + hour)
req.session.cookie.maxAge = hour

For example when maxAge is set to 60000 (one minute), and 30 seconds has elapsed it will return 30000 until the current request has completed, at which time req.session.touch() is called to reset req.session.maxAge to its original value.

req.session.cookie.maxAge // => 30000

Every session store must implement the following methods

• .get(sid, callback)
• .set(sid, session, callback)
• .destroy(sid, callback)

Recommended methods include, but are not limited to:

• .length(callback)
• .clear(callback)

For an example implementation view the connect-redis repo.