[voraa]

Нормальное
Но можно было и так

let nextSlide = function(){
    if (index == slides.length - 1){
        index = 0;
        activeSlide(index);
        activedots(index);
    }
    else{
        index++;
        activeSlide(index);
        activedots(index);
    }
	clearInterval(interval);
}
next.addEventListener("click", nextSlide);
 
let prevSlide = function(){
    if (index == 0){
        index = slides.length -1;
        activeSlide(index);
        activedots(index);
    }
    else{
        index--;
        activeSlide(index);
        activedots(index);
    }
	clearInterval(interval);
}
prev.addEventListener("click", prevSlide);