fetch('/api/someData', {
    method : "GET",
})
.then(......)

app.get('/api/:blah', (req, res, next) => {
    if(logged in or authenticated user){
        next()
    } else {
        res.redirect('someReAuthPage')
    }
})


app.get('/api/someData', (req, res) => {
    ..........
    res.json('someJsonData')
}