Simple and Modern LazyLoad

lazyload.js

// https://twitter.com/samccone/status/1200967148580921344?s=20

this.obs = new IntersectionObserver(onHit, {
  rootMargin: '0px',
  threshold: 0.2
});

this.obs.observe(elms);

onHit(entries) {
  for (const e of entries) {
    if (e.isIntersecting) { // GO }
}