How can I use Node.js Express-session inside a conditional middleware? - node.js

Question

var express = require('express')
var parseurl = require('parseurl')
var session = require('express-session')
var app = express()
app.use(session({
secret: 'keyboard cat',
resave: false,
saveUninitialized: true
}))
This is my simple code. However, I want to use session only if the req.url contains /web. Is there a way I can wrap this inside a middleware of my own?
I've tried:
function setSession(req,res,next){
if(req.url.indexOf('/api') != 0){
app.use(session({
secret: 'keyboard cat',
resave: false,
saveUninitialized: true
}));
next();
}else{
next();
}
};
and then
app.use(setSession);
But setting req.session.hello = "world" in my controller gives: TypeError: Cannot set property 'hello' of undefined. Simply put, it doesn't work. Are my arguments wrong in my middleware?

Answer 1

However, I want to use session only if the req.url contains /web. Is there a way I can wrap this inside a middleware of my own?
You certainly can. You can use express.Router to create sub-routes, like this:
var sessionMiddleware = session({
secret: 'keyboard cat',
resave: false,
saveUninitialized: true
});
var webRoutes = express.Router()
.get('/', function(req, res, next) {
res.send('I have a session!');
});
var nonWebRoutes = express.Router()
.get('/', function(req, res, next) {
res.send('No session here');
});
app.use('/web', express.Router()
.use(sessionMiddleware)
.use(webRoutes));
app.use('/nonweb', nonWebRoutes);
Edit:
If however you want to conditionally execute the middleware function, you could do it like this:
app.use(function(req, res, next) {
if (req.url.indexOf('/api') !== 0) {
sessionMiddleware(req, res, next);
} else {
next();
}
});
app.get('/api', function(req, res, next) {
res.send(!!req.session); //false
});
app.get('/web', function(req, res, next) {
res.send(!!req.session); //true
});
But I prefer the sub-route approach because it maps your path route structure to a hierarchy which makes the code easier to read and easier to incorporate other middleware that make use of sessions, like passport.js for example.