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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

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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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Packages

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

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HTML 

              
                <h1 class="title">Simple JavaScript Tab Bar</h1>
<div class="container">
  <ul class="container__list">
    <li class="container__item container__item_active">
      <span class="container__link">Intro</span>
    </li>
    <li class="container__item">
      <span class="container__link">HTML</span>
    </li>
    <li class="container__item">
      <span class="container__link">CSS</span>
    </li>
    <li class="container__item">
      <span class="container__link">JavaScript</span>
    </li>
    <li class="container__item">
      <span class="container__link">Animation</span>
    </li>
  </ul>
  <div class="container__inner">
    <h2 class="content__subtitle">Intro</h2>
    <p class="content__description">
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Fugit, illum ipsam nesciunt nisi perferendis quisquam repellendus reprehenderit voluptatum? A cupiditate, deleniti doloremque hic iste praesentium quia quidem quisquam sunt vel.
    </p>
  </div>
  <div class="container__inner container__inner_hidden">
    <h2 class="content__subtitle">HTML</h2>
    <p class="content__description">
      The HyperText Markup Language, or HTML(HyperText Markup Language) is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaScript.
    </p>
  </div>
  <div class="container__inner container__inner_hidden">
    <h2 class="content__subtitle">CSS</h2>
    <p class="content__description">
      Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation of a document written in a markup language such as HTML. CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript.
    </p>
  </div>
  <div class="container__inner container__inner_hidden">
    <h2 class="content__subtitle">JavaScript</h2>
    <p class="content__description">
      JavaScript, often abbreviated as JS, is a programming language that conforms to the ECMAScript specification. JavaScript is high-level, often just-in-time compiled and multi-paradigm. It has dynamic typing, prototype-based object-orientation and first-class functions.
    </p>
  </div>
  <div class="container__inner container__inner_hidden">
    <h2 class="content__subtitle">Animation</h2>
    <p class="content__description">
      CSS animations make it possible to animate transitions from one CSS style configuration to another. Animations consist of two components, a style describing the CSS animation and a set of keyframes that indicate the start and end states of the animation’s style, as well as possible intermediate waypoints.
    </p>
  </div>
</div>
!

CSS 

              
                html,
body {
  width: 100%;
  height: 100%;
}

body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
  font-family: "Ubuntu", Arial, sans-serif;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  background: radial-gradient(
    circle,
    rgba(239, 241, 173, 1) 3%,
    rgba(160, 195, 237, 1) 100%
  );
}

.title {
  margin: 30px 0;
  padding: 0;
  color: #4c6067;
  font-size: 36px;
  line-height: 36px;
  letter-spacing: 1px;
  font-weight: 700;
  text-rendering: optimizeLegibility;
}

.container {
  width: 100%;
  min-height: 270px;
  max-width: 800px;
  background: #fff;
  border-radius: 10px;
  padding: 20px;
  box-sizing: border-box;
  box-shadow: rgba(33, 35, 38, 0.1) 0 10px 10px -10px;
}

.container__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-rows: repeat(1, minmax(min-content, max-content));
  grid-template-columns: repeat(5, minmax(min-content, max-content));
  grid-auto-rows: minmax(min-content, max-content);
  grid-auto-columns: minmax(min-content, max-content);
  justify-content: space-around;
  gap: 10px 20px;
}

.container__item {
  width: 100px;
  color: #4c6067;
  min-height: 30px;
  border-radius: 3px;
  display: grid;
  justify-content: center;
  align-content: center;
  cursor: pointer;
  position: relative;
  font-size: 16px;
  line-height: 16px;
  letter-spacing: 1px;
  font-weight: 400;
  transition: 0.2s;
}

.container__item::after {
  content: "";
  display: block;
  position: absolute;
  width: 40%;
  margin: 0 30%;
  bottom: 0;
  border-bottom: 1px solid #4c6067;
}

.container__item_active {
  background: #4c6067;
  box-sizing: border-box;
  color: #ebfaff;
  font-weight: 300;
}

.container__link {
  margin: 0;
  padding: 0;
}

.container__inner {
  width: 80%;
  margin: 45px auto 35px;
}

.content__subtitle {
  animation-name: smoothTop;
  animation-duration: 0.3s;
  font-size: 22px;
  line-height: 22px;
  font-weight: 500;
  color: #404648;
}

.content__description {
  animation-name: smoothBottom;
  animation-duration: 0.7s;
  font-size: 14px;
  line-height: 22px;
  font-weight: 300;
  color: #404648;
}

.container__inner_hidden {
  display: none;
}

@keyframes smoothTop {
  0% {
    opacity: 0.2;
    transform: translateY(7%);
  }
  100% {
    opacity: 1;
    transform: translateY(0%);
  }
}

@keyframes smoothBottom {
  0% {
    opacity: 0.2;
    transform: translateY(-3%);
  }
  100% {
    opacity: 1;
    transform: translateY(0%);
  }
}
!

JS 

              
                let tabContent = document.querySelectorAll(".container__inner");
let tabItem = document.querySelectorAll(".container__item");

// For each element with class 'container__item'
for (let i = 0; i < tabItem.length; i++) {
  // if the element was hovered
  //you can replace mouseover with click
  tabItem[i].addEventListener("mouseover", () => {
    // Add to all containers class 'container__inner_hidden'
    tabContent.forEach((item) => {
      item.classList.add("container__inner_hidden");
    });
    // Clean all links from class 'container__item_active'
    tabItem.forEach((item) => {
      item.classList.remove("container__item_active");
    });
    // Make visible correct tab content and add class to item
    tabContent[i].classList.remove("container__inner_hidden");
    tabItem[i].classList.add("container__item_active");
  });
}
!
999px

Console