express-session not persisting through pages - node.js

Question

I've made a basic website with nodejs and express that needs a session system so i used express-session to do that. The issue is that my session is not kept through the different pages of my website, it seems like the req.session is directly deleted after the login has been done.
Here is my code (just the important parts):
var express = require('express');
var consolidate = require('consolidate');
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/mydb";
var bodyparser = require('body-parser');
var session = require('express-session');
//var MongoStore = require('connect-mongo')(session);
var app = express();
app.engine('html', consolidate.swig);
app.set('view engine', 'html');
app.use(express.static(__dirname + '/views'));
app.use(bodyparser.json());
app.use(bodyparser.urlencoded({extended:true}));
app.use(session({
secret: "stfkjvctygf",
resave : false,
saveUninitialized : true,
cookie: { secure: false, maxAge: 1800000 }
}));
app.post('/login',function(req,res,next){
MongoClient.connect(url, function(err, db){
if(err) throw err;
var dbo=db.db("testdb");
var user=dbo.collection("login").findOne({userid : req.body.userid, pwd : req.body.pwd}, function(err, user){
if(err) throw err;
if (user) {
req.session.user = user;
req.session.save(function() {
console.log("current user session: "+req.session.user.userid);
res.render('mainpage.html', {userid: req.session.user.userid});
});
}
else {
console.log("connection failed");
res.render('login.html', {error: 'Invalid username or password'});
}
db.close();
});
});
});
app.get('/mainpage', function(req,res,next) {
if (req.session.user) {
res.render('mainpage.html', {userid: req.session.user.userid});
}
else {
return res.status(401).send();
}
});
app.get('/profilpage', function(req,res,next){
res.render('profilpage.html', {userid: req.session.user.userid});
});
app.listen(8080);
So when the log in of an user succeeds, mainpage.html is displayed properly (the field userid is correctly field with req.session.user.userid), but when I click on another page like the profilpage or if I come back to the mainpage, the session is not saved and the userid field is incorrect.
I also want to mention that the if (req.session.user) clause
in /mainpage does not work, the else seems to be never used.
(The mongodb database and html files are correct)
Thank you.

Answer 1

Delete 'var user =' because you dont need to assign the query to a variable since it is using a callback for returned data.
dbo.collection("login").findOne({userid : req.body.userid, pwd : req.body.pwd}, function(err, user){
if(err) throw err;
console.log(user) //It is most likely an array. Then use index to point the session to the username as such req.session.user = user[0].username
if (user) {
req.session.user = user;
req.session.save(function() {
console.log("current user session: "+req.session.user.userid);
res.render('mainpage.html', {userid: req.session.user.userid});
});
}
else {
console.log("connection failed");
res.render('login.html', {error: 'Invalid username or password'});
}
In addition, 'if(user)' is a bad practice, because if mongodb returns an empty array, that condition is still true, so that causes error in your logic. Its better to do something like
if(data.length > 0){
//your code here. data is what is returned from your mongo Query
}