Express 4.x Updated Answer
Session handling is no longer built into Express. This answer refers to the standard session module: https://github.com/expressjs/session
To clear the session data, simply use:
req.session.destroy();
The documentation is a bit useless on this. It says:
Destroys the session, removing req.session, will be re-generated next request.
req.session.destroy(function(err) {
// cannot access session here
})
This does not mean that the current session will be re-loaded on the next request. It means that a clean empty session will be created in your session store on next request. (Presumably the session ID isn’t changing, but I have not tested that.)