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HTML

About HTML Preprocessors

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

In CodePen, whatever you write in the HTML editor is what goes within the <body> tags in a basic HTML5 template. So you don't have access to higher-up elements like the <html> tag. If you want to add classes there that can affect the whole document, this is the place to do it.

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.

!
Insecure Resource

The resource you are linking to is using the 'http' protocol, which may not work when the browser is using https.

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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You can apply CSS to your Pen from any stylesheet on the web. Just put a URL to it here and we'll apply it, in the order you have them, before the CSS in the Pen itself.

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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.

Add External Scripts/Pens

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You can apply a script from anywhere on the web to your Pen. Just put a URL to it here and we'll add it, in the order you have them, before the JavaScript in the Pen itself.

If the script you link to has the file extension of a preprocessor, we'll attempt to process it before applying.

You can also link to another Pen here, and we'll pull the JavaScript from that Pen and include it. If it's using a matching preprocessor, we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency.

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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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About Packages

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.

All packages are different, so refer to their docs for how they work.

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HTML 

              
                <p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Assumenda adipisci quia aut facilis, commodi rem debitis culpa. Dolorem, doloremque, odio, omnis dolores itaque praesentium laudantium velit nostrum labore recusandae molestias?</p>
<p>Inventore aperiam eligendi minima nisi consectetur recusandae numquam alias dignissimos repellat corporis asperiores, animi earum, odit suscipit aliquid? Tempore quasi molestiae eligendi accusantium possimus voluptatum nesciunt animi libero earum aspernatur.</p>
<p>Repudiandae nulla natus dignissimos sapiente velit minima quam odio explicabo, nobis ipsa obcaecati libero unde nam soluta, voluptatibus quia accusantium, modi reiciendis culpa deleniti atque. Tempore voluptatibus autem officia illum.</p>
<p>Libero aspernatur excepturi quaerat soluta numquam repellendus fuga ipsam eveniet quidem a laudantium nulla magni, dolorum optio repudiandae maxime odit aliquid laboriosam nostrum modi, eos commodi sapiente accusamus. Ullam, quis?</p>
<p>Neque pariatur molestias possimus amet, provident nam! Dolores, inventore. Inventore voluptatibus, dolorem in ipsum laboriosam consequatur iure maiores nobis saepe rem autem, quisquam amet, error repudiandae eum itaque assumenda voluptatem.</p>
<p>Ab tempore, asperiores laudantium adipisci delectus labore velit recusandae eos eveniet reprehenderit sit, voluptates ducimus nulla voluptas et reiciendis ex doloribus nemo explicabo possimus dolor id molestiae. Enim, similique quaerat!</p>
<p>Dolorem quas asperiores odit sint ut quia neque molestias voluptates, adipisci distinctio vero aperiam ipsa accusantium aliquam veritatis magnam labore, officia perferendis quasi beatae cumque expedita tenetur pariatur. Saepe, error.</p>
<p>Perferendis velit molestiae earum vero suscipit minus? Officiis odit facere laudantium quibusdam nemo impedit similique, eum voluptates fugit, tempora distinctio delectus ut consequatur nihil quo, maiores eaque blanditiis perferendis omnis?</p>
<p>Earum doloribus asperiores iusto iure facere atque molestiae? Hic assumenda ratione sequi, illo vero soluta accusantium reprehenderit quisquam corrupti magnam pariatur voluptates dicta doloribus illum sed ipsum et molestiae explicabo.</p>
<p>Qui tenetur ducimus temporibus laborum magnam iure corporis eius nesciunt nisi excepturi explicabo, obcaecati enim quod et est illo adipisci expedita iste cum nam. Labore possimus autem similique dolorum tempore.</p>
<p>Sapiente voluptatum fugiat ipsam sunt a distinctio temporibus aliquam cupiditate amet? Expedita recusandae autem eius porro esse, libero assumenda adipisci fugit aspernatur odit dolorum optio earum fugiat, vero minus debitis!</p>
<p>A aspernatur officia, iusto numquam architecto doloremque pariatur alias tenetur commodi quo doloribus delectus sed impedit, quidem odit. Enim illum natus nemo quasi aspernatur voluptatibus ea exercitationem eos alias et.</p>
<p>Reiciendis impedit libero ipsum ullam nulla hic nesciunt blanditiis at necessitatibus quae magnam animi, vel ipsam placeat. Accusamus ex quam molestiae, esse eveniet vitae adipisci minus voluptate enim sapiente iure!</p>
<p>Labore voluptas nisi ex sit repellendus dolorem dolores excepturi cum, omnis, aperiam quisquam eius, modi iusto consequatur velit ipsa cupiditate. Culpa molestias dicta non mollitia distinctio nesciunt, eaque omnis possimus!</p>
<p>Facere fuga minima blanditiis rem necessitatibus asperiores omnis. Possimus repellat, veritatis modi saepe molestiae, magni dolorum nam ullam exercitationem doloremque quod, consequuntur corporis reprehenderit id illum hic nulla sequi eius.</p>
<p>Asperiores magni ad deleniti vel aperiam inventore illo blanditiis accusamus quidem quam? Fuga odio optio, eligendi sit soluta nulla libero, voluptatem corrupti commodi assumenda itaque in possimus esse consequuntur animi.</p>
<p>Beatae quidem quos illum exercitationem neque, ea saepe cupiditate molestiae, possimus, corrupti numquam excepturi temporibus officiis quibusdam. Soluta pariatur qui, aut, inventore eaque necessitatibus eius alias excepturi earum veritatis omnis.</p>
<p>Molestias mollitia cupiditate optio provident enim, reiciendis tempore veritatis fugiat voluptate harum saepe nihil cumque vitae minus architecto tempora maxime necessitatibus quos eveniet suscipit aut. Non ipsam dolorum ipsum ut.</p>
<p>Architecto porro minima, quae distinctio debitis est velit deserunt eaque perspiciatis veniam sint praesentium placeat voluptatum, esse iure dolor enim ad commodi tempore! Deserunt iste voluptatum pariatur doloremque perferendis voluptates!</p>
<p>Qui quisquam ex excepturi delectus culpa veniam nemo iste cum vitae natus! Omnis totam vitae, cum asperiores id nemo voluptatum ut facilis nihil! Autem, libero neque blanditiis aspernatur tempora eveniet.</p>
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CSS 

              
                body {
  max-width: 500px; 
  margin: 0 auto;
  font: 17px/1.4 system-ui;
}
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JS 

              
                const scrollElement = (element, scrollPosition, duration) => {
  
  // useful while testing to re-run it a bunch.
  // element.removeAttribute("style"); 
  
  const style = element.style;
  style.transition = duration + 's';
  style.transitionTimingFunction = 'ease-in-out';
  style.transform = 'translate3d(0, ' + -scrollPosition + 'px, 0)';
}

scrollElement(
  document.body, 
  (
    document.body.getBoundingClientRect().height
    -
    document.documentElement.clientHeight
    +
    25
  ),
  5
);
!
999px

Console