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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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Adding Classes

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About the <head>

In CodePen, whatever you write in the HTML editor is what goes within the <body> tags in a basic HTML5 template. If you need things in the <head> of the document, put that code here.

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Insecure Resource

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CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

We offer two popular choices: Autoprefixer (which processes your CSS server-side) and -prefix-free (which applies prefixes via a script, client-side).

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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Using packages here is powered by esm.sh, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ESM usage.

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HTML 

              
                <main class="Loop js-loopContainer">
  <section class="js-loopItem green">
    <h1>One</h1>
  </section>
  <section class="js-loopItem red">
    <h1>For</h1>
  </section>
  <section class="js-loopItem blue">
    <h1>All</h1>
  </section>
  <section class="js-loopItem orange">
    <h1>And</h1>
  </section>
  <section class="js-loopItem blue">
    <h1>All</h1>
  </section>
  <section class="js-loopItem red">
    <h1>For</h1>
  </section>
</main>
!

CSS 

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

.Loop {
  position: relative;
  height: 100%;
  overflow: auto;
  -webkit-overflow-scrolling: touch;
}

section {
  position: relative;
  text-align: center;
  /* height: clamp(300px, 80%, 700px) */
  min-height: 300px;
  max-height: 700px;
  height: 80%;
}





/* To hide the scrollbar */

/*
.Loop {
  scrollbar-width: none;
}

.Loop::scrollbar {
  display: none;
}
*/




/* Demo styles */

body {
  font-family: "Avenir Next", Helvetica, sans-serif;
  font-weight: normal;
  font-size: 100%;
}

.red {
  background: #FF4136;
}
.green {
  background: #2ECC40;
}
.blue {
  background: #0074D9;
}
.orange {
  background: rebeccapurple;
}

h1 {
  margin: 0;
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 100%;
  font-size: 80px;
  letter-spacing: 5px;
  color: #fff;
  text-transform: uppercase;
}
!

JS 

              
                var doc = window.document,
  context = doc.querySelector('.js-loopContainer'),
  items = doc.querySelectorAll('.js-loopItem'),
  clones = [],
  disableScroll = false,
  scrollHeight = 0,
  scrollPos = 0,
  clonesHeight = 0

function getScrollPos () {
  return (context.pageYOffset || context.scrollTop) - (context.clientTop || 0)
}

function setScrollPos (pos) {
  context.scrollTop = pos
}

function getClonesHeight () {
  clonesHeight = 0

  Array.from(clones, clone => {
    clonesHeight = clonesHeight + clone.offsetHeight
  })

  return clonesHeight
}

function reCalc () {
  scrollPos = getScrollPos()
  scrollHeight = context.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 () {
      disableScroll = false
    }, 40)
  }
}

function onLoad () {
  Array.from(items, item => {
    const clone = item.cloneNode(true)
    context.appendChild(clone)
    clone.classList.add('js-clone')
  })

  clones = context.querySelectorAll('.js-clone')

  reCalc()

  context.addEventListener('scroll', function () {
    window.requestAnimationFrame(scrollUpdate)
  }, false)

  window.addEventListener('resize', function () {
    window.requestAnimationFrame(reCalc)
  }, false)
}

window.onload = onLoad
!
999px

Console