How to know if user is logged in with passport.js?

If user is logged in, passport.js will create user object in req for every request in express.js, which you can check for existence in any middleware:

if (req.user) {    // logged in} else {    // not logged in}

You can create simple express.js middleware for that, that will check if user is logged in, and if not - will redirect to /login page:

function loggedIn(req, res, next) {    if (req.user) {        next();    } else {        res.redirect('/login');    }}

And use it:

app.get('/orders', loggedIn, function(req, res, next) {    // req.user - will exist    // load user orders and render them});

If you would like to use it in your templates as your code sample seems to indicate you can create some middleware such as this:

app.use(function (req, res, next) {  res.locals.login = req.isAuthenticated();  next();});

Place that code somewhere after you have setup passport.

And then use it in your template (swig example)

{% if login %}<button>logout</button>{% else %} <button>login</button>{% endif %}

It is not explicitly documented but there is a isAuthenticated() method which is inserted into req by passport.
Can be used as follows,

req.isAuthenticated() // returns true if auth, false if not

// auth.jsmodule.exports = {  ensureAuthenticated: (req, res, next) => {    if (req.isAuthenticated()) {      return next()    }    res.redirect('/login') // if not auth  },  forwardAuthenticated: (req, res, next) => {    if (!req.isAuthenticated()) {      return next()    }    res.redirect('/dashboard');  // if auth      }}

// app.jsapp.get('/dashboard', ensureAuthenticated, (req, res) => res.render('dashboard'))app.get('/login', forwardAuthenticated, (req, res) => res.render('login'))app.get('/register', forwardAuthenticated, (req, res) => res.render('register'))