javascript - .join() function cant load and be defined in jQuery -

here url: http://itsun.ir/test/ first excuse bad english, want add drag , drop layout wordpress theme, seems good, when li element move other columns, javascript should make cookie , save new positions load in other time, doesn't work correctly, when open resources tab in inspect element in chrome browser , move , li sortable item column , in resources panel occurs error said : [uncaught typeerror : object # has no method 'join' ] , have updated jquery doesn't make correct, can me out writting in correct way ???

      <script type="text/javascript">  $(document).ready(function(){  // items function getitems(id) {     return $('#' + id + '-list').sortable('toarray').join(','); 

uncaught typeerror: object # has no method 'join'

}  // load items cookie function loaditemsfromcookie(name) {     if ( $.cookie(name) != null )     {         renderitems($.cookie(name),"wrapp");     }     else     {         alert('cookie "' + name + '" not set');     } }  // render items function renderitems(id, itemstr) {     var list = $('#' + id + '-list');     var items = itemstr.split(',')      ( var in items )     {         html = '<li class="sortable-item';          if ( id == 'wrapp' )         {             html += ' columns';         }         html += '" id="' + items[i] + '"><div class="loader"></div></li>';          list.append(html);          // load html file         $('#' + items[i]).load('content/' + items[i] + '.html');     }    }  // load items cookie or defaults var defaults = [];  defaults['splash'] = 'rightc,centerc,leftc'; var splashsource = ( $.cookie('splash-cookie') == null ) ? defaults['splash'] : $.cookie('splash-cookie'); renderitems('splash', splashsource);   // splash (top) $('#wrapp .sortable-list').sortable({     forcehelpersize: true,     forceplaceholdersize: true,     handle: '.label',     containment: '#wrapper',     opacity: 0.8,     placeholder: 'placeholder',     connectwith: '#wrapper .sortable-list',     update: function(){         $.cookie('splash-cookie', getitems('splash'));     } });             });         </script>