$carousel.on( 'change.flickity', function( event, index ) {
console.log( 'Slide changed to ' + index )
});
<div class="carousel-cell black is-selected" aria-selected="true" style="position: absolute; left: 100%;"></div>
<div class="carousel-cell black is-selected" aria-selected="true" style="position: absolute; left: 100%;"></div>
<div class="carousel-cell black is-selected" aria-selected="true" style="position: absolute; left: 100%;"></div>