app.use(function(req, res, next) {
  res.locals.user = req.session.user;
  next();
});

/*


You can use res.locals to expose particular data to all templates.

In your situation, you could add the following middleware to Express:


This will make a user variable available in all your templates.

You do need to make sure that you add that middleware after req.session has been set (which is usually after express-session has been added to the middleware chain).
*/