AJAX：如何发布空数组？

i have an associative array with lists. Take a look at the following JSON:

console.log(JSON.stringify(fields);

Output

{
  "sb1":[],
  "sb2":["val1","val2","val3"],
  "sb3":["val1","val2","val3"]
}

As you can see, array-entry "sb1" is empty. Array "sb1" disappear while posting var "fields" to PHP.

Here is a code-snippet:

$(document).ready(function() {
  $("#button").click(function(e) {
    e.preventDefault();
    var fields = {};
//The following saves selectboxes and options in var fields//
    $("select").each(function() {
      var $select = $(this);
      fields[$select.attr('name')] = $select.find('option').map(function() {
        return $(this).val();
      }).get();
    });

    var jsonObj = fields;
    var jsonStringify = JSON.stringify(fields);
    console.log("JSON.stringify(fields): " + jsonStringify);
//Result is OK

    $.ajax({
      url: "saveJson.php",
      type: "post",
      data: { jsonStringify : jsonStringify },
      success: function (response) {
        console.log("data transmitted: " + response);
//Response doesnt transmit empty arrays!
      },
      error: function(jqXHR, textStatus, errorThrown) {
        console.log(textStatus, errorThrown);
      }
    });
  });
});

Your javascript code send the empty array. If you want to have the empty array in the response of your request, you have to modify the code of your server.