const imageCount = 3

const slidePhoto = (imageCount) => {
  let count = 1;
  let photoUlTag = document.querySelector(".visual_img");
  for (var i=0; i<imageCount; i++) {
    photoUlTag.children[i].style.width = photoUlTag.offsetWidth + "px";
  }

  photoUlTag.style.left = "0px";
  photoUlTag.style.transition = "2s ease-out";
  photoUlTag.style.width = photoUlTag.offsetWidth*imageCount + "px";
  
  setInterval(() => {
   photoUlTag.style.left = (parseFloat(photoUlTag.style.left) - (photoUlTag.offsetWidth / imageCount)) + "px";
   count++;
   
   if (count > imageCount) {
    count = 1;
    photoUlTag.style.left = "0px";
   }
  }, 3300);
}

slidePhoto(imageCount)