jquery validate ajax submit form

when the jquery validation plugin is used for validating the form data, such as below:

html code:

<form method="post" action="" id="buy-form" novalidate="novalidate">
                    <table style="margin:35px 150px 0 150px;">
                        <tr>
                            <td class="info-title">预定版本<input type="hidden" name="versionName" id="versionName" value="" /></td>
                            <td class="info-content-version">免费版本</td>
                        </tr>
                        <tr>
                            <td class="info-title">联系人</td>
                            <td class="info-content"><p><input class="required" type="text" placeholder="请输入联系人姓名（必填）" style="width:330px;" name="name" id="applicants-name" /></p></td>
                        </tr>
                        <tr>
                            <td class="info-title">电话</td>
                            <td class="info-content"><input type="text" placeholder="座机区号" style="width:100px;" name="locationNo" id="locationNo" /> - <input type="text" placeholder="座机号码/手机号码（必填）" style="width:209px;" name="phone" id="phone" /></td>
                        </tr>
                        <tr>
                            <td class="info-title">邮箱</td>
                            <td class="info-content"><input type="text" placeholder="请输入联系人邮箱地址（必填）" style="width:330px;" name="email" id="email" /></td>
                        </tr>
                        <tr>
                            <td class="info-title">公司名称</td>
                            <td class="info-content"><input type="text" placeholder="请输入联系人公司名称（必填）" style="width:330px;" name="companyName" id="companyName" /></td>
                        </tr>
                    </table>
                </form>

js code:

var form = $("#buy-form");
        form.validate({
            errorElement: "span",
            rules: {
                "name": {
                    required: true
                },
                "phone": {
                    required: true
                },
                "email": {
                    required: true
                },
                "companyName": {
                    required: true
                }
            },
            messages: {
                "name": {
                    required: "请输入联系人姓名",
                },
                "phone": {
                    required: "请输入号码",
                },
                "email": {
                    required: "请输入邮箱地址",
                },
                "companyName": {
                    required: "请输入公司名称",
                }
            }
        });

ajax submit code:

        $(".submit").click(function(){

            var form = $("#buy-form");
            var $alertDialog = $("#alert-dialog");

            form.submit(function (event) { event.preventDefault();});//阻止在数据校验失败的情况下提交表单；绑定事件，但不触发；
            form.submit();//触发绑定事件；
            var validator = form.validate();
            if (validator.numberOfInvalids() <= 0) {//判断加入所有校验都通过后再做ajax提交；
                $.ajax({
                    url: "Home/SubmitPurchaseApplication",
                    data: $("#buy-form").serialize(),
                    type: "post",
                    async: false,
                    success: function (data) {
                        freeDialog.dialog("close");
                        $("#alert-title h3").text("购买成功！");
                        $("#alert-message p").text("您的购买申请已经提交，我们会尽快联系您");
                        ShowAlertDialog(); //异步提交后弹框提示；

                    },
                    error: function () {
                        freeDialog.dialog("close");
                        $("#alert-title h3").text("购买失败！");
                        $("#alert-message p").text("您的购买申请出现异常，请重新申请");
                        ShowAlertDialog();
                    }
                });
            }
        });