一次显示警报并突出显示字段

Question

我正在使用JQuery-validate插件来验证表单。到目前为止，只要出现错误，我都会突出显示这些字段。我希望显示警报，指示有一些错误需要更正，但是我不确定在哪里添加警报。无论我将其添加到现有代码中的哪个位置，它都会多次显示。

$(function() {

    $("form[id='changeAccountSettings']").validate({

      onclick: false,
      onkeyup: false,
      errorPlacement: function(error, element) {

        var n = element.attr("name");

        if (n == "first_name")
            element.attr("placeholder", "Please provide a first name");
        else if (n == "last_name")
            element.attr("placeholder", "Please provide a last name");  
        else if (n == "email")
      element.attr("placeholder", "Valid email address");
      else if (n == "cellphone")
            element.attr("placeholder", "Valid cellphone number");

    },
    rules: {
        first_name: {
            minlength: 2,
            required: true
        },
        last_name: {
            minlength: 2,
            required: true
        },
        email: {
            minlength: 6,
            required: true,
            email: true
        },
        cellphone: {
          minlength: 10,
          required: true,
          number: true
      },

    },
    highlight: function(element) {

        $(element).addClass('has_error');

    },
    unhighlight: function(element) {

        $(element).removeClass('has_error');
    },
    submitHandler: function(form) {
        form.submit();

    }

});
  });