exposed-collapsible.js

(function($) {

  /**
   * Change multi-value dropdown to single-value dropdown and back (visually).
   */
  Drupal.behaviors.collapsibleFilterRewriteMultipleSelect = {
    attach: function(context, settings) {
      $.each(Drupal.settings.collapsibleFilter.multiple_selects, function(name, settings) {
        $('select#edit-' + name)
              .once('collapsible-filter-multiple-rewrite')
              .each(function() {

          var selectionCount = $('option:selected', $(this)).length;
          if (selectionCount <= 1) {
            // Set size of select to 1 if there is not more than 1 selected.
            $(this).attr('size', 1);
            // Remove attribute "multiple".
            $(this).removeAttr('multiple');
            // Set default option.
            if (selectionCount === 0 || $(this).val() === 'All') {
              $(this).val('All');
            }

            // Add link to expand the dropdown.
            $expand = $('<a>')
                    .addClass('select-expander')
                    .attr('href', '#')
                    .attr('title', Drupal.t('Expand selection'))
                    .html('[+]')
                    .click(function() {
                      // Get corresponding select element.
                      $select = $(this)
                              .parent('.form-type-select')
                              .find('.collapsible-filter-multiple-rewrite-processed');
                      // Expand element.
                      $select.attr('size', settings.size)
                              .attr('multiple', 'multiple');
                      $(this).remove();
                    })
                    .appendTo($(this).parent());
          }
        });
      });
    }
  };

})(jQuery);