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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-.

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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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HTML 

              
                <h2>Toggle Switch</h2>
<p id="version">Last updated in <a href="https://cdn.watermarkinsights.com/css/rc/1.1.7/wm-global.css" target="blank">rc 1.1.7</a></p>
<p>Toggle switches may be in one of two positions, usually on or off. Behind the scenes they are marked up as checkboxes.</p>
<p>The HTML structure consists of a container <code>label</code> element with an <code>input</code> followed by a corresponding element with the accessible name and an optional element with text for the state, e.g. ON/OFF. If using the state, you will need to write a script for the onchange event.</p>
<label class="switch-toggle" for="toggle">
  <input type="checkbox" id="toggle">
  <div class="togglelabel">Label for toggle</div>
  <div class="toggletext">off</div>
</label>

<h3>Previous Implementation</h3>
<p>As with the implementation above, our original implementation uses the label to create the visual switch. However, we would add a second label to associate an accessible name with the checkbox. According to web.dev this actually <em>created</em> an accessibility issue, and Lighthouse will flag it as a problem: </p>
<blockquote>If you unintentionally associate multiple labels with a single control, you'll create inconsistent behavior across browsers and assistive technologies: some will read the first label, some will read the last label, and others will read both labels.</blockquote>
<div class="toggle-switch">
  <input type="checkbox" id="oldtoggle">
  <label class="switchtoggle" for="oldtoggle" data-checked="ON"></label>
  <label for="oldtoggle">We shouldn't do this</label>
</div>
!

CSS 

              
                html, body {
  height: auto;
}
body {
  padding: 0 20px 40px;
  font-size: 14px;
}
h2 {
  font-size: 24px;
  font-weight: 600;
  margin-bottom: 0;
  
  &:not(:first-of-type) {
    margin-top: 32px;
  }
  
  + p {
    margin-top: 0;
  }
}
h3 {
  font-size: 22px;
  font-weight: 400;
  margin: 32px 0 0;
  
  + p {
    margin-top: 0;
  }
}

blockquote {
  margin-left: 0;
  padding-left: 20px;
  border-left: 4px solid #e9e7ec;
}

#version {
  font-style: italic;
}
!

JS 

              
                const textcontainer = document.querySelector('.toggletext')
document.getElementById('toggle').addEventListener('change', c =>  c.target.checked ? textcontainer.innerHTML = 'on'
  : textcontainer.innerHTML = 'off'
  )
!
999px

Console