Passing variables to the next middleware using next() in Express.js
This is what the res.locals object is for. Setting variables directly on the request object is not supported or documented. res.locals is guaranteed to hold state over the life of a request.
An object that contains response local variables scoped to the request, and therefore available only to the view(s) rendered during that request / response cycle (if any). Otherwise, this property is identical to app.locals.
This property is useful for exposing request-level information such as the request path name, authenticated user, user settings, and so on.
app.use(function(req, res, next) { res.locals.user = req.user; res.locals.authenticated = !req.user.anonymous; next();});To retrieve the variable in the next middleware:
app.use(function(req, res, next) { if (res.locals.authenticated) { console.log(res.locals.user.id); } next();});
Attach your variable to the req object, not res.
Instead of
res.somevariable = variable1;Have:
req.somevariable = variable1;As others have pointed out, res.locals is the recommended way of passing data through middleware.
I don't think that best practice will be passing a variable like req.YOUR_VAR. You might want to consider req.YOUR_APP_NAME.YOUR_VAR or req.mw_params.YOUR_VAR.
It will help you avoid overwriting other attributes.
Update May 31, 2020
res.locals is what you're looking for, the object is scoped to the request.
An object that contains response local variables scoped to the request, and therefore available only to the view(s) rendered during that request / response cycle (if any). Otherwise, this property is identical to app.locals.
This property is useful for exposing request-level information such as the request path name, authenticated user, user settings, and so on.