IntersectionObserver 曝光

const io = new IntersectionObserver((entries) => {
  entries.forEach((e) => {
    if (e.isIntersecting) {
      e.target.classList.add('visible');
      io.unobserve(e.target);
    }
  });
});
document.querySelectorAll('.lazy').forEach((el) => io.observe(el));