jquery - 追加は、送信時にすべての空の入力フィールドに適用されるわけではありません

Answer 1

Do this way:-

$("#submit").click(function(){
    $("input[class='required']").each(function(){
          if ($.trim($(this).val()).length == 0)               
              $(this).val('Not Applicable');
    });
});

Once validation is OK then go for submitting the form.

Answer 2

I think I may have worked it out - can you confirm if this logic is correct?

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

 $("input[class='required']").each(function(){

      if ($.trim($(this).val().length == 0) && $(this).attr('disabled'))

         $(this).val('Not Applicable');    

      });

 });