Zoom & Fade In Elements On Scroll

A smooth scrolling interaction concept that zooms & fades in/out elements on vertical page scrolling using the requestAnimationFrame API and CSS3 transforms.

See It In Action:

See the Pen
Smooth card scrolling interaction! ✨ by Colin van Eenige (@cvaneenige)
on CodePen.

How to use it:

1. Create elements on the page.

<div class="box">Box 1<div>
<div class="box">Box 2<div>
<div class="box">Box 3<div>
<div class="box">Box 4<div>
<div class="box">Box 5<div>
...

2. The main JavaScript to enable the smooth scrolling interactions on the elements.

requestAnimationFrame(() => {
  const boxes = document.querySelectorAll(".box");
  function getIntersectionRatio(i) {
    const a = [window.scrollY, window.scrollY + window.innerHeight];
    const b = [boxes[i].offsetTop, boxes[i].offsetTop + boxes[i].clientHeight];
    const max = Math.max(a[0], b[0]);
    const min = Math.min(a[1], b[1]);
    return Math.max(0, (min - max) / (b[1] - b[0]));
  }
  function onScroll() {
    const boxes = document.querySelectorAll(".box");
    for (let i = 0; i < boxes.length; i += 1) {
      const intersection = getIntersectionRatio(i);
      const top = boxes[i].offsetTop - window.pageYOffset < 0;
      boxes[i].firstChild.style.cssText = `
        transform-origin: ${top ? "center center" : "top center"};
        position: ${top ? "fixed" : "absolute"};
        transform: scale(${intersection});
        opacity: ${intersection};
      `;
    }
    requestAnimationFrame(onScroll);
  }
  onScroll();
});