西安腾讯云web前端面试

document.addEventListener("DOMContentLoaded", function() {
  let lazyImages = [].slice.call(document.querySelectorAll("img.lazy"));
  if ("IntersectionObserver" in window) {
    let lazyImageObserver = new IntersectionObserver(function(entries, observer) {
      entries.forEach(function(entry) {
        if (entry.isIntersecting) {
          let lazyImage = entry.target;
          lazyImage.src = lazyImage.dataset.src;
          lazyImage.classList.remove("lazy");
          lazyImageObserver.unobserve(lazyImage);
        }
      });
    });
    lazyImages.forEach(function(lazyImage) {
      lazyImageObserver.observe(lazyImage);
    });
  }
});

fetch('https://api.example.com/data', {
  method: 'GET',
  mode: 'cors', // no-cors, *cors, same-origin
  headers: {
    'Content-Type': 'application/json'
  }
})
.then(response => response.json())
.then(data => console.log(data))
.catch((error) => console.error('Error:', error));