better_way.js

    self.add_state(new FreeText(
        "reg_school_classrooms",
        "reg_school_teachers",
        "How many classrooms do you have in your school?"
    ));

    self.add_creator('reg_school_teachers', function(state_name, im) {
        var input = parseInt(im.get_user_answer('reg_school_classrooms'));
        if (!isNaN(input)) {
            return new FreeText(
                "reg_school_teachers",
                "reg_school_teachers_g1",
                "How many teachers in total do you have in your school?"
            );
        } else {
            return self.make_bad_data_state(
                'reg_school_classrooms_error',
                'reg_school_classrooms',
                'a number');
        }
    });

    self.add_creator('reg_school_classrooms_error', function(state_name, im) {
        return self.make_bad_data_state(
                'reg_school_classrooms_error',
                'reg_school_classrooms',
                'a number');
    });