nodejs express.router with parameters - node.js

Question

Problem
I am using a nodejs application with the express module. To have a structure I split the routes into a extern routes.js. I want give this route.js next to the req and res parameters some other parameters who will be needed. But I don´t know how I can do it.
Index.js
const app = express();
app.use(session({
secret: uuidv4(),
resave: true,
saveUninitialized: true
}));
app.use(helmet());
app.use(cors());
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({
extended: true
}));
app.use('/', express.static(path.join(__dirname, '/site/static')));
app.use('/', routes);
routes.js
module.exports = (function() {
'use strict';
let router = require('express').Router();
router.get('/', (req, res) => {
if(!req.session || req.session.key !== loginkey) {
res.redirect('/login');
} else {
res.redirect('dashboard');
};
});
router.get('/dashboard', (req, res) => {
if(req.session && req.session.key === loginkey) {
helper.render(req, res, "sites/dashboard");
} else {
res.redirect('/');
};
});
router.get('/login', (req, res) => {
log.LogLine(3, "GET /login");
helper.render(req, res, "sites/login");
});
router.get('/logout', (req, res, next) => {
log.LogLine(3, "GET /logout");
if (req.session) {
req.session.destroy(function(err) {
if(err) {
return next(err);
} else {
return res.redirect('/');
};
});
};
});
return router;
})();

Answer 1

If you want to pass something along from index.js to your routes in routes.js then you can do the following.
In your routes.js, you could accept some parameters:
module.exports = function(arg1, arg2) {
let router = require('express').Router();
router.get('/', (req, res) => {
// You can now use arg1 and arg2 here
});
// ...
return router;
};
Note, you'll need to remove your IIFE to stop the function from being immediately invoked.
Then in index.js, you can invoke the function and pass in whatever you want:
app.use('/', routes('something', 'something else'));
I hope this helps.