Uncaught ReferenceError: titlesArr is not defined что за ошибка ?

if ($('[data-date]').length > 0) {
        var toGroup = $('[data-date]'),
            group = {};
        toGroup.each(function(){
           group[$(this).data('date')] = '';
        });
        for (date in group) {
          toGroup.filter('[data-date='+ date +']').wrapAll('<div class="group"></div>').eq(0).before('<div class="group-name"><div>'+titlesArr[0]+date+'</div></div>');
        }
    };