キーボード操作を追加したカルーセルのサンプル

← →

<div class="carousel-outer">
  <div class="carousel">
    <div class="carousel__section">
      <img src="https://placehold.jp/ccffff/000000/960x540.png?text=Section1">
    </div>
    <div class="carousel__section">
      <img src="https://placehold.jp/ffccff/000000/960x540.png?text=Section2">
    </div>
    <div class="carousel__section">
      <img src="https://placehold.jp/ccffcc/000000/960x540.png?text=Section3">
    </div>
  </div>
  <button class="carousel__button-left">←</button>
  <button class="carousel__button-right">→</button>
</div>

img {
  max-width: 100%;
  height: auto;
}

.carousel-outer {
  position: relative;
  overflow: hidden;
  width: 100%;
  max-width: 960px;
}

.carousel {
  display: flex;
  transform: translateX(0);
}

.carousel__section {
  min-width: 100%;
}

.carousel__button-left,
.carousel__button-right {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  cursor: pointer;
}

.carousel__button-left {
  left: 5%;
}

.carousel__button-right {
  right: 5%;
}

let current = 1
let isAnimation = false;
const carousel = document.querySelector('.carousel')
const carousels = document.querySelectorAll('.carousel__section')
const carouselLen = carousels.length
const lastCarousel = carouselLen + 1
const total = carouselLen + 2;
const newOrder = [];

newOrder.push(carousels[carouselLen - 1].outerHTML)
carousels.forEach((section) => {
  newOrder.push(section.outerHTML)
})
newOrder.push(carousels[0].outerHTML)
carousel.innerHTML = newOrder.join('')

function showSection() {
  isAnimation = true;
  carousel.style.transform = `translateX(${-current * 100}%)`;
}

function prevSection() {
  if (isAnimation) return

  current = current === 0 ? carouselLen + 1 : current - 1;
  showSection()
}

function nextSection() {
  if (isAnimation) return

  current = (current + 1) % (carouselLen + 2);
  showSection()
}

const btnLeft = document.querySelector('.carousel__button-left')
const btnRight = document.querySelector('.carousel__button-right')

btnLeft.addEventListener('click', prevSection)
btnRight.addEventListener('click', nextSection)

carousel.addEventListener('transitionend', () => {
  if (current === carouselLen + 1) {
    current = 1
  } else if (current === 0) {
    current = carouselLen
  }

  carousel.classList.add('no-transition')
  carousel.style.transform = `translateX(${-current * 100}%)`
  setTimeout(() => {
    carousel.classList.remove('no-transition')
    isAnimation = false
  }, 20)
})

function handleKeyDown(event) {
  if (isAnimation) return

  if (event.key === 'ArrowLeft') {
    prevSection()
  } else if (event.key === 'ArrowRight') {
    nextSection()
  }
}

document.addEventListener('keydown', handleKeyDown)

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