Ajax request problem-Maximum call stack size exceeded

Good afternoon,

I have this simple code below using js but it returns me the error that is in the print below:

Note: I am using CodeIgniter 3.0.10, AJAXm jQuery 3.0.0 Minifed and Bootstrap 4

* * Code: *

        jQuery(document).ready(function() {

                var base = $("#base_url").val();
                $('#telefone').mask('(99) 99999-9999');

            jQuery("#form-registrar-estilo").submit(function(e) {

                e.preventDefault();

                var email_validar = $("#email").val();

                for (let el of jQuery('#form-registrar-estilo input')) {
                        if (el.value == "") el.classList.add("error");
                        else el.classList.remove("error");
                    }


                if (!jQuery('#form-registrar-estilo input.error').length) {
                        jQuery.ajax({
                        url:  base + "painel/cadastrar/valida_email",
                        type: "POST",
                        data: {email:email},
                        dataType: "json",

                        success: function(data) {
                            alert(data);
                        }


                    })
                };
            });
        });