jquery.validate 动态增加、删除规则

<form name="form" id="form1">
        <table>
            <tr>
                <td>类型：</td>
                <td>
                    <select name="type" id="type">
                            <option value="">请选择</option>
                            <option value="1">身份证</option>
                            <option value="2">护照</option>
                        </select>
                </td>
            </tr>
            <tr>
                <td>号码：</td>
                <td><input type="text" name="code" id="code"></td>
            </tr>
            <tr>
                <td colspan="2">
                    <input type="submit" value="提交">
                </td>
            </tr>
        </table>
    </form>

$(function(){
        /***** add/remove rule*****/
         $("#type").change(function(){
             $("#code").rules("remove");
             if($(this).val()=="1"){
                 $("#code").rules("add",{required:true,minlength:6,messages:{required:"请输入正确身份号"}});
             }else if($(this).val()=="2"){
                 $("#code").rules("add",{required:true,minlength:3,messages:{required:"请输入正确护照号"}});
             }
         });

         $("#form1").validate({
               errorPlacement: function (lable, element)
                {
                    lable.appendTo(element.parent());
                },
                success: function (lable)
                {
                    lable.remove();
                },
                submitHandler: function (form)
                {
                    console.log("form submit");
                }
         });
    });