jQuery extension Multiple Select Toggle

gistfile1.js

// Add a clickable plus (+) sign after a select element that when clicked
// toggles the multiple attribute on the select box
// obviously it could use some options for the toggle element, styling or
// the select size
(function($){
  $.fn.extend({
    multiSelectToggle : function(options){
                          //Settings list and the default values
                          var defaults = {
                                label: '+'
                            };

                          var options = $.extend(defaults, options);

                          $('._multi_select_toggle').live('click', function(e){
                              var selector = $(this).prev('select');
                              selector.attr('multiple', !selector.attr('multiple'));
                            })
                            var span = $('<span />').text(options.label).addClass('_multi_select_toggle').css('cursor', 'pointer');
                            $(this).after(span);
                          }
  });
})(jQuery);

// where needed
$(function($){
  $('#my_select').multiSelectToggle();
  $('.many_selects').multiSelectToggle({label: 'Expand'});
});