.bgi {
      width: 200px;
      height: 200px;
      background-size: cover;
    }

const Bgi = document.querySelectorAll('.bgi');
const defaultImg = 'https://i.imgur.com/4aYifFs.jpeg';

Bgi.forEach((item) => {
  const bgiItem = item.style.backgroundImage.split('(')[1].split(')')[0];
  const image = new Image();
  image.src = bgiItem.replace(/\"/g, '');
  if (!image.complete) {
    item.style.backgroundImage = `url(${defaultImg})`;
  }
  image.onload = () => {
    console.log('圖片正確')
  };
});