How can I implement checking if the user is logged in Express.js?

Question

Express.js

Good afternoon, I got such a check, but I don’t like it at all, because this check must be specified in each route. Is there any way to take this out to another file and correct it. I do everything through the passport module. Maybe you can somehow display this in passport serialize?

router.get('/', async(req, res) => {
    if (req.user !== undefined) {
        authenticate = true
    } else {
        authenticate = false
    }
    res.render('index', {
        titlePage: 'Asd',
        auth: authenticate,
        user: req.user
    })
})

passport.serializeUser(function(user, done) {
    done(null, user);
})

passport.deserializeUser(function(obj, done) {
    done(null, obj);
});

function ensureAuthenticated(req, res, next) {
    if (req.isAuthenticated()) { return next() }
    res.redirect('/')
    console.log('Для того, чтобы зайти в профиль авторизируйтесь')
}

You can not offer this, as I understand it, the function checks whether the user is logged in, but it is intended to enter the page, and I need to display the elements on the site. Or am I just misunderstanding and this function can be used as a login check?