layout.html.slim

    = javascript_tag nonce: true do
      ' (function() {
      '   const images = [...document.querySelectorAll("img")];
      '   let count = 0;
      '
      '   const ready = () => {
      '     const div = document.createElement("div");
      '     div.id = "HCTIReadyNow";
      '     document.body.appendChild(div);
      '   };
      '
      '   const onLoad = () => {
      '     count += 1;
      '     if (count >= images.length) {
      '       ready()
      '     }
      '   };
      '
      '   images.forEach((image) => {
      '     image.onload = onLoad;
      '
      '     if (image.complete && image.naturalHeight !== 0) {
      '       count += 1;
      '     } 
      '   });
      '
      '   if (images.length === count) {
      '     ready()
      '   }
      ' })()