js FormData

gistfile1.js

            /* form submit*/
            $(function() {
                $("form").first().submit(function(e) {
                    e.preventDefault();
                    var form = $(this);
                    if (form) {
                        var url = form.attr("action");
                        var formData = new FormData(document.forms[0]);
                        $.ajax({
                            url: url,
                            type: 'POST',
                            data: formData,
                            processData: false,
                            contentType: false,
                            success: function(data) {
                                $('#dialog').html(data);
                            },
                            error: function() {
                                alert("Errore del server");
                            }
                        })
                    }
                });
            });

thanks