导入默认图片;

import defaultImg from "@/assets/images/200.png";
export default {
  install(Vue) {
    // // 注册自定义指令   v2方法
    Vue.directive("lazy", {
      // inserted () {
      //   console.log(11111)
      // }
      //注册自定义指令  v3方法
      mounted(el, binding) {
        // 浏览器提供 IntersectionObserver
        const observer = new IntersectionObserver(
          ([{ isIntersecting }]) => {
            // console.log(isIntersecting, '====IntersectionObserver')
            if (isIntersecting) {
              console.log(el, binding, 11111);
              // 图片加载失败就显示默认图片
              el.onerror = function () {
                el.src = defaultImg;
              };
              el.src = binding.value;
              // 不在监听dom
              observer.unobserve(el);
            }
          },
          {
            threshold: 0.01,
          }
        );
        // 监听dom
        observer.observe(el);
      },
    });
  },
};