Twitter Bootstrap Carousel - access current index

Instead of adding and subtracting from the current slide, try this on the 'slide' event:

$('.carousel').on('slide',function(e){
    var slideFrom = $(this).find('.active').index();
    var slideTo = $(e.relatedTarget).index();
    console.log(slideFrom+' => '+slideTo);
});

It appears Bootstrap 4 finally has the native implementation of this.

https://github.com/twbs/bootstrap/pull/21668

$('#myCarousel').on('slide.bs.carousel', function(e){
  e.direction     // The direction in which the carousel is sliding (either "left" or "right").
  e.relatedTarget // The DOM element that is being slid into place as the active item.
  e.from          // The index of the current item.     
  e.to            // The index of the next item.
});

This worked for me (Bootstrap 3)

$("#myCarousel").on('slide.bs.carousel', function(evt) {
  console.debug("slide transition started")
  console.debug('current slide = ', $(this).find('.active').index())
  console.debug('next slide = ', $(evt.relatedTarget).index())
})