Using the form's submit event to set a flag might work for you.
var formHasChanged = false;
var submitted = false;
$(document).on('change', 'form.confirm-navigation-form input, form.confirm-navigation-form select, form.confirm-navigation-form textarea', function (e) {
formHasChanged = true;
});
$(document).ready(function () {
window.onbeforeunload = function (e) {
if (formHasChanged && !submitted) {
var message = "You have not saved your changes.", e = e || window.event;
if (e) {
e.returnValue = message;
}
return message;
}
}
$("form").submit(function() {
submitted = true;
});
});