$form['arrival_date'] = [
  '#type'                => 'date_popup',
  '#title'               => t('Arrival date'),
  '#date_format'         => 'd/m/Y',
  '#date_year_range'     => '0:+1',
  '#date_label_position' => 'none',
  '#default_value'       => '',
  '#size'                => '10',
];

(function ($) {

  Drupal.behaviors.ios2 = {
    attach: function (context, settings) {
      $('#edit-arrival-date-datepicker-popup-1').datepicker('option', {
        onClose: function (date) {
          // date will have the new date or empty string if no date
          // has been selected.
          alert(date);
          // Do something
        }
      });
    }
  };

})(jQuery);

$('#edit-arrival-date-datepicker-popup-1').datepicker({

(function ($) {

  Drupal.behaviors.ios2 = {
    attach: function (context, settings) {
      $('#edit-arrival-date-datepicker-popup-1').datepicker({
        onClose: function (date) {
          // date will have the new date or empty string if no date
          // has been selected.
          alert(date);
          // Do something
        }
      });
    }
  };

})(jQuery);