bbh-pc/script/image_switch.js

let controls = document.querySelectorAll('.exhibition');

for(let control of controls){

    let part = control.querySelectorAll('.cards'),
    partLength = part.length;
    console.log("partLength",partLength);
    let partArray = [].slice.call(part);
    let indexicon = control.querySelectorAll('.index div');
    let currentIndex = 0;
    let nextbutton = control.querySelector(".next");

    control.addEventListener("click",function(e){
        let target = e.target;
        
        if(target.classList.contains("next")){
            let next = e.target,
                currentPart = partArray[currentIndex],
                nextPart = partArray[(currentIndex+1)%partLength],
                currentIndexIcon = indexicon[currentIndex],
                nextIndexIcon = indexicon[(currentIndex+1)%partLength];
    
    
            currentPart.classList.add("disappear");
            nextPart.classList.remove("disappear");
            currentIndexIcon.classList.remove("index_on");
            nextIndexIcon.classList.add("index_on");
            currentIndex = (currentIndex+1)%partLength;
            console.log("next",currentIndex);
    
        }
    });
}