boostrap判斷當前slider的index
$('#carousel-id').on('slide.bs.carousel', function (e) {        var active = $(e.target).find('.carousel-inner > .item.active');        var from = active.index();        var next = $(e.relatedTarget);        var to = next.index();         to=to+1;         // console.log(from + ' => ' + to);      });