Parallax and Loop

by jacob_truax

HTML

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
  <link rel="stylesheet" href="normalize.css">
  <link rel="stylesheet" href="style.css">
  <script src="https://cdnjs.cloudflare.com/ajax/libs/gsap/2.0.2/TweenMax.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/gsap/2.1.2/TimelineMax.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.0/jquery.min.js"></script>
</head>

<body>
<main>
<div class="Loop js-loop">

<section>

  <div class="info">
    <h2>Hello 1</h2>
    <p>Hello 1</p>
  </div>
</section>

<section>

  <div class="info">
    <h2>Hello 2</h2>
    <p>Hello 2</p>
  </div>
</section>

<section>

  <div class="info">
    <h2>Hello 3</h2>
    <p>Hello 3</p>
  </div>
</section>

<section>

  <div class="info">
    <h2>Hello 4</h2>
    <p>Hello 4</p>
  </div>
</section>

<section>

  <div class="info">
    <h2>Hello 5</h2>
    <p>Hello 5</p>
  </div>
</section>

<section>

  <div class="info">
    <h2>Hello 6</h2>
    <p>Hello 6</p>
  </div>
</section>

<section>

  <div class="info">
    <h2>Hello 7</h2>
    <p>Hello 7</p>
  </div>
</section>

<section>

  <div class="info">
    <h2>Hello 8</h2>
    <p>Hello 8</p>
  </div>
</section>



<!--
  These blocks are the same as the first blocks to get that looping illusion going.
  You need to add clones to fill out a full viewport height.
  -->

  <section class="is-clone">

    <div class="info">
      <h2>Hello 1</h2>
      <p>Hello 1</p>
    </div>
  </section>

  <section class="is-clone">

    <div class="info">
      <h2>Hello 2</h2>
      <p>Hello 2</p>
    </div>
  </section>


</div>
</main>

</body>

CSS

html,
body {
  height: 100%;
  /* overflow: hidden; */
}

body {
  color: #000;
}

main {
  height: 100%;
  position: relative;
  top: 0;
  left: 0;
}

header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  text-align: center;
  z-index: 1;
}

.Loop {
  position: absolute;
  height: 100%;
  overflow: auto;
}

section {
  position: relative;
  display: flex;
  flex-direction: row;
  align-items: center;
  justify-content: center;
  width: 100vw;
  height: 100vh;
}

::scrollbar {
  display: none;
}

section div {
  position: absolute;
  z-index: 2;
  text-align: center;
  width: 50%;
  background-color: #ff0000;
}

section img {
  position: relative;
  width: 50%;
  background-color: #000;
}

JavaScript

const sections = document.querySelectorAll("section")
const divTag = document.querySelector("div.Loop")
const mainTag = document.querySelector("main")

var doc = window.document,
  clones = divTag.querySelectorAll('.is-clone'),
  disableScroll = false,
  scrollHeight = 0,
  scrollPos = 0,
  clonesHeight = 0,
  i = 0;

const addMovement = function() {
  const topViewport = divTag.scrollTop
  const midViewport = topViewport + (divTag.offsetHeight / 2)

  sections.forEach(section => {
    const topSection = section.offsetTop
    const midSection = topSection + (section.offsetHeight / 2)

    const distanceToSection = (midViewport - midSection)
    console.log(distanceToSection)

    const image = section.querySelector(".info")

    image.style.transform = `rotate(${distanceToSection}deg)`
  })
}

addMovement()

function getScrollPos () {
  return (divTag.offsetTop || divTag.scrollTop) - (divTag.clientTop || 0);
}

function setScrollPos (pos) {
  divTag.scrollTop = pos;
}

function getClonesHeight () {
  clonesHeight = 0;

  for (i = 0; i < clones.length; i += 1) {
    clonesHeight = clonesHeight + clones[i].offsetHeight;
  }

  return clonesHeight;
}

function reCalc () {
  scrollPos = getScrollPos();
  scrollHeight = divTag.scrollHeight;
  clonesHeight = getClonesHeight();

  if (scrollPos <= 0) {
    setScrollPos(1); // Scroll 1 pixel to allow upwards scrolling
  }
}

function scrollUpdate () {
  if (!disableScroll) {
    scrollPos = getScrollPos();

    if (clonesHeight + scrollPos >= scrollHeight) {
      // Scroll to the top when you’ve reached the bottom
      setScrollPos(1); // Scroll down 1 pixel to allow upwards scrolling
      disableScroll = true;
    } else if (scrollPos <= 0) {
      // Scroll to the bottom when you reach the top
      setScrollPos(scrollHeight - clonesHeight);
      disableScroll = true;
    }
  }

  if (disableScroll) {
    // Disable scroll-jumping for a short time to avoid flickering
    window.setTimeout(function () {
     ...