expressjs.com/en/api/res-locals.jade

section
  h3(id='res.locals') res.locals

  p.
    Response local variables are scoped to the request, thus only
    available to the view(s) rendered during that request / response
    cycle, if any. Otherwise this API is identical to <a href="#app-locals">app.locals</a>.

  p.
    This object is useful for exposes request-level information such as the
    request pathname, authenticated user, user settings etcetera.

  +js.
    app.use(function(req, res, next){
      res.locals.user = req.user;
      res.locals.authenticated = ! req.user.anonymous;
      next();
    });