How to create plugin with ajax response

How to create plugin with ajax response

Plugin Code
  1. (function($) {
  2.     $.fn.dateSlider = function($options) {
  3.         var $defaults = {
  4.             page: ''
  5.         };

  7.         var $settings = $.extend({}, $defaults, $options);

  9.         return this.each(function() {
  10.             $.post($settings.page, function($res) {
  11.                 $settings.done.call(this);
  12.             });
  13.         });
  14.     };
  15. }(jQuery));
html

  1.         $(function() {
  2.             $('.test').dateSlider({
  3.                 page: 'res.php',
  4.                 done: function() {
  5.                     // want to do something when ajax send data back
  6.                 }
  7.             });
  8.         });

Plugin will connect to res.php and get the data back names $res, how to send the result to function named done?