function clamp(min, val, max) { if (val < min) { val = min; } if (val > max) { val = max; } return val; } const scrollchecks = () => { var el = document.getElementById("header"); el.style.backgroundPositionY = 50 + (document.documentElement.scrollTop/el.scrollHeight) / 2 * 100 + "%"; Array.from(document.getElementsByClassName("scrolly")).forEach(el => { let box = el.getBoundingClientRect(); if (box.bottom < 0 || box.top >= window.innerHeight) { el.classList.add("scrolly-out"); el.classList.remove("scrolly-in"); el.classList.remove("scrolly-onedge"); } else { el.classList.remove("scrolly-out"); el.classList.add("scrolly-in"); el.classList.add("scrolly-entered"); if (box.top <= 0 || box.bottom >= window.innerHeight) { el.classList.add("scrolly-onedge"); } else { el.classList.remove("scrolly-onedge"); } } if (box.top + box.height / 2 <= window.innerHeight / 2) { el.classList.add("scrolly-tophalf"); el.classList.remove("scrolly-bottomhalf"); } else { el.classList.remove("scrolly-tophalf"); el.classList.add("scrolly-bottomhalf"); } }); var perc = clamp(0, document.getElementById("outer").scrollTop / (window.innerHeight / 2), 1); document.querySelector("#headin > h1").style.fontSize = 2 + 4 * (1 - perc) + "em"; document.querySelector("#links").style.opacity = perc; }; window.addEventListener("scroll", scrollchecks); window.addEventListener("scrollend", scrollchecks); window.addEventListener("wheel", scrollchecks); window.addEventListener("resize", scrollchecks); window.addEventListener("load", scrollchecks); setInterval(scrollchecks, 250); // Computers are fast and scrolling in JavaScript is dumb. Shoot me.