Pen Settings

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.

Learn more · Versions

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.

Learn more · Versions

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).

Add External Stylesheets/Pens

Any URLs added here will be added as <link>s in order, and before the CSS in the editor. You can use the CSS from another Pen by using its URL and the proper URL extension.

Powered by Algolia
About External Resources

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.

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

Learn more

+ add another resource

JavaScript

About JavaScript Preprocessors

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

Learn more · Versions

Babel includes JSX processing.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

Powered by Algolia
About External Resources

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.

Learn more

+ add another resource

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.

Powered by Algolia
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.

If you're using React / ReactDOM, make sure to turn on Babel for the JSX processing.

Behavior

Auto Save

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.

HTML 

              
                main
  .accordion
    .accordion-item
      .accordion-header
        h2 Lorem ipsum dolor sit amet 1
      .accordion-body
        p 1 Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
        
    .accordion-item
      .accordion-header
        h2 Lorem ipsum dolor sit amet 2
      .accordion-body
        p 2 Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
        
        
    .accordion-item
      .accordion-header
        h2 Lorem ipsum dolor sit amet 3
      .accordion-body
        p 3 Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
        
  .credits
    p Animation inspired by: 
      a(href="https://dribbble.com/hellobaha" target="_blank") Bakhtiyar 😱 Sattarov
!

CSS 

              
                @import url('https://fonts.googleapis.com/css?family=Roboto:400,500')

*
  box-sizing: border-box

$blue: #2b42b6
$border-radius: 5px

body, html
  width: 100%
  height: 100%
  font-family: 'Roboto', sans-serif

main
  width: 100%
  min-height: 100%
  display: flex
  justify-content: center
  align-items: flex-start
  background-color: $blue
  padding: 150px 30px
  
.accordion
  max-width: 550px

  &-item
    background-color: transparent
    margin-bottom: 15px
    border-radius: $border-radius
    box-shadow: 0 2px 9px 0 rgba(black, .1)
    transition: background-color .2s ease-in .3s

    &.active
      background-color: white
      transition: background-color .2s ease-in 0s

      .accordion
        &-header
          color: black
          background-color: white
          transition: background-color .2s ease-in 0s, color .2s ease-in .2s
          
          h2
            &:before, &:after
              background-color: black
              transition: background-color .2s ease-in .2s, transform .2s ease .1s
            &:before
              display: none
            
            &:after
              transform: rotate(90deg)

        &-body
          max-height: 900px
          padding: 0 15px 15px
          transition: max-height .3s ease-in 0s, padding .2s ease-in 0s
          
          p
            opacity: 1
            transition: opacity .2s ease-in .2s

  &-header
    color: white
    background-color: lighten($blue, 15%)
    border-radius: $border-radius
    padding: 25px 15px
    cursor: pointer
    transition: background-color .2s ease-out .3s, color .2s ease-out 0s

    h2
      position: relative
      font-size: 1rem
      font-weight: 500
      letter-spacing: .025em
      margin: 0

      &:before, &:after
        content: ""
        position: absolute
        background-color: white
        transition: background-color .2s ease-in 0s, transform .2s ease 0s
      
      &:before
        width: 10px
        height: 2px
        right: 0
        top: calc(50% - 1px)
      
      &:after
        width: 2px
        height: 10px
        right: 4px
        top: calc(50% - 5px)
        transform: none

  &-body
    max-height: 0
    padding: 0 15px
    overflow: hidden
    transition: max-height .2s ease-out 0s, padding .1s ease-out .2s

    p
      font-size: .875rem
      line-height: 1.6
      opacity: 0
      margin: 0
      transition: opacity .2s ease-in 0s
      
.credits
  position: absolute
  bottom: 30px
  right: 30px
  font-size: 14px
  p
    color: lighten($blue, 30%)
    margin: 0
  a
    color: white
!

JS 

              
                const accordionItem = document.querySelectorAll('.accordion-item');
                             
const onClickAccordionHeader = e => {
  if (e.currentTarget.parentNode.classList.contains('active')) {
    e.currentTarget.parentNode.classList.remove("active");
  } else {
    Array.prototype.forEach.call(accordionItem, e => e.classList.remove('active'));
    e.currentTarget.parentNode.classList.add("active");
  }
};

const init = () => {
  Array.prototype.forEach.call(accordionItem, e => e.querySelector('.accordion-header').addEventListener('click', onClickAccordionHeader, false));
};

document.addEventListener('DOMContentLoaded', init);
!
999px

Console