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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

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.

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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).

Add External Stylesheets/Pens

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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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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 

              
                <div class="accordion-container">
  <h2>jQuery Accordion</h2>
  <div class="set">
    <a href="#">
      Vestibulum 
      <i class="fa fa-plus"></i>
    </a>
    <div class="content">
      <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna.</p>
    </div>
  </div>
  <div class="set">
    <a href="#">
      Phasellus 
      <i class="fa fa-plus"></i>
    </a>
    <div class="content">
      <p> Aliquam cursus vitae nulla non rhoncus. Nunc condimentum erat nec dictum tempus. Suspendisse aliquam erat hendrerit vehicula vestibulum.</p>
    </div>
  </div>
  <div class="set">
    <a href="#">
      Praesent 
      <i class="fa fa-plus"></i>
    </a>
    <div class="content">
      <p>Pellentesque aliquam ligula libero, vitae imperdiet diam porta vitae. sed do eiusmod tempor incididunt ut labore et dolore magna.</p>
    </div>
  </div>
  <div class="set">
    <a href="#">
      Curabitur 
      <i class="fa fa-plus"></i> 
    </a>
    <div class="content">
      <p> Donec tincidunt consectetur orci at dignissim. Proin auctor aliquam justo, vitae luctus odio pretium scelerisque. </p>
    </div>
  </div>
</div>
!

CSS 

              
                body{
  background-color: #567;
  padding: 0 10px;
  font-family: 'Open Sans', sans-serif;
}
.accordion-container{
  position: relative;
  max-width: 500px;
  height: auto;
  margin: 10px auto;
}
.accordion-container > h2{
  text-align: center;
  color: #fff;
  padding-bottom: 5px;
  margin-bottom: 20px;
  padding-bottom: 15px;
  border-bottom: 1px solid #ddd;
}
.set{
  position: relative;
  width: 100%;
  height: auto;
  background-color: #f5f5f5;
}
.set > a{
  display: block;
  padding: 10px 15px;
  text-decoration: none;
  color: #555;
  font-weight: 600;
  border-bottom: 1px solid #ddd;
  -webkit-transition:all 0.2s linear;
  -moz-transition:all 0.2s linear;
  transition:all 0.2s linear;
}
.set > a i{
  float: right;
  margin-top: 2px;
}
.set > a.active{
  background-color:#3399cc;
  color: #fff;
}
.content{
  background-color: #fff;
  border-bottom: 1px solid #ddd;
  display:none;
}
.content p{
  padding: 10px 15px;
  margin: 0;
  color: #333;
}
!

JS 

              
                $(document).ready(function() {
  $(".set > a").on("click", function() {
    if ($(this).hasClass("active")) {
      $(this).removeClass("active");
      $(this)
        .siblings(".content")
        .slideUp(200);
      $(".set > a i")
        .removeClass("fa-minus")
        .addClass("fa-plus");
    } else {
      $(".set > a i")
        .removeClass("fa-minus")
        .addClass("fa-plus");
      $(this)
        .find("i")
        .removeClass("fa-plus")
        .addClass("fa-minus");
      $(".set > a").removeClass("active");
      $(this).addClass("active");
      $(".content").slideUp(200);
      $(this)
        .siblings(".content")
        .slideDown(200);
    }
  });
});
!
999px

Console