https://www.mailboxvalidator.com/includes/js/lazyloadyoutube.js

1document.addEventListener("DOMContentLoaded", function() {
2  let lazyYoutubes = [].slice.call(document.querySelectorAll("div.youtube"));
3  let active = false;
4
5  const lazyLoadYoutube = function() {
6    if (active === false) {
7      active = true;
8
9      setTimeout(function() {
10        lazyYoutubes.forEach(function(lazyYoutube) {
11          if ((lazyYoutube.getBoundingClientRect().top <= window.innerHeight && lazyYoutube.getBoundingClientRect().bottom >= 0) && getComputedStyle(lazyYoutube).display !== "none") {
12            // videos[i].style.backgroundImage = 'url(https://i.ytimg.com/vi/' + videos[i].id + '/sddefault.jpg)';
13            lazyYoutube.style.backgroundImage = lazyYoutube.dataset.src;
14            // lazyYoutube.classList.add(lazyYoutube.dataset.src);
15            // lazyYoutube.srcset = lazyYoutube.dataset.srcset;
16            // lazyYoutube.classList.remove("lazy");
17
18            lazyYoutubes = lazyYoutubes.filter(function(image) {
19              return image !== lazyYoutube;
20            });
21
22            if (lazyYoutubes.length === 0) {
23              document.removeEventListener("scroll", lazyLoadYoutube);
24              window.removeEventListener("resize", lazyLoadYoutube);
25              window.removeEventListener("orientationchange", lazyLoadYoutube);
26            }
27          }
28        });
29
30        active = false;
31      }, 200);
32    }
33  };
34
35  document.addEventListener("scroll", lazyLoadYoutube);
36  window.addEventListener("resize", lazyLoadYoutube);
37  window.addEventListener("orientationchange", lazyLoadYoutube);
38});