JS Document height

height.js

// Calculation on load because otherwise IOS devices return an unreliable height variable ( different values at different places )
window.addEventListener("load", () => {
  // See stackoverflow post https://stackoverflow.com/a/1147768
  let height = Math.max(
    document.body.scrollHeight,
    document.body.offsetHeight,
    html.clientHeight,
    html.scrollHeight,
    html.offsetHeight
  );
});

scroll-listener.js

// If scroll direction is upwards, and we are not at the bottom 15px
if (
      window.pageYOffset < lastKnownScrollPosition &&
      window.innerHeight + window.pageYOffset <= height - 15
)