var swiper = new Swiper('.swiper-container', {
        pagination: '.swiper-pagination',
        slidesPerView: 1,
        paginationClickable: true,
        spaceBetween: 30,
        loop: true,
        onSlideChangeEnd: function(swiper){
          console.log(swiper.activeIndex) //每次切换时，提示现在是第几个slide
          changeBg((swiper.activeIndex) % 5);
        }
    });
 
    // 回调切换背景
    function changeBg(index){
        $('#main').removeClass().addClass(function(){
            switch (index) {
                case 0:
                    return 'bg-5';
                    break;
                case 6:
                    return 'bg-1';
                    break;
                default:
                    return 'bg-'+index;
                    break
            }
        });
    }