I'm a newbie at node.js, and trying to make a login page.

When I'm trying to login with the right credentials the page works as intended. Also worth noting is that when I try to login with no credentials the alert window pops up. But when I try to login with the wrong credentials, it just won't work. I've tracked the error back to "alert" function, but I cannot understand why in the world the alert function works when calling it to display the alert that no username nor password was inserted, but will crash when I'm trying to display that the username and password are wrong. I'm pretty certain that the error comes from the alert function.

The code is below.

Thanks alot!

app.post('/auth', function(request, response) {
var username = request.body.username;
var password = request.body.password;
if (username && password) {
    connection.query('SELECT * FROM accounts WHERE username = ? AND password = ?', [username, password], function(error, results, fields) {
        if (results.length > 0) {
            request.session.loggedin = true;
            request.session.username = username;
            response.redirect('/home');
            response.end();
        } else {
            alert('Incorrect Username and/or Password!');
        }
    });
} else {
    alert('Please enter Username and Password!');
}
});