Абра Кадабра

$(document).ready(function($) {                    
                    $('#fullpage').fullpage({
                      anchors: ['firstPage', 'secondPage', '3rdPage', '4thPage'],
                      menu: '#menu',
                      afterLoad: function(anchorLink, index){
                          if(anchorLink == 'secondPage'){
                              $('.about_section').addClass('a_vis');
                            $('.about_section').addClass('animated fadeInUp');
                          }
                          if(anchorLink == '3rdPage'){
                            $('.services_content').addClass('animated fadeInDown');
                          }
                      },
                    }); 
        });