ice.fo.utils/Window/waitForElementOnScreen.js

export default function waitForElementOnScreen(el) {
  return new Promise((resolve) => {
    const observer = new IntersectionObserver((entries) => {
      // Use `intersectionRatio` because of Edge 15's
      // lack of support for `isIntersecting`.
      // See: https://github.com/w3c/IntersectionObserver/issues/211
      if (entries[0].intersectionRatio <= 0) { return; }

      // Cleanup the observer when it's not
      // needed anymore.
      observer.unobserve(el);

      resolve();
    });

    // Begin observer
    try {
      observer.observe(el);
    } catch (error) {
      resolve();
    }
  });
}