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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

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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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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HTML 

              
                <main>
  <h1>There can be only one</h1>
<div>
<form action="" method="get">
  
  <h2>Basic <code>select</code></h2>
<p>
  <label for="fruit">What’s your favorite fruit?</label>
  <select name="fruit" id="fruit">
    <option>Apple</option>
    <option>Orange</option>
  </select>
</p>

<h2>Different value</h2>
<p>
  <label for="location">Where are you?</label>
  <select name="location" id="location">
    <option value="US">United States</option>
    <option value="non-US">Outside the United States</option>
  </select>
</p>

<h2>Empty default choice</h2>
<p>
  <label for="fruit_2">What’s your favorite fruit?</label>
  <select name="fruit_2" id="fruit_2">
    <option value="">-- Choose One --</option>
    <option>Apple</option>
    <option>Orange</option>
  </select>
</p>
  
<h2>Pre-selected option</h2>
<p>
  <label for="fruit_3">What’s your favorite fruit?</label>
  <select name="fruit_3" id="fruit_3">
    <option value="">-- Choose One --</option>
    <option>Apple</option>
    <option selected>Orange</option>
  </select>
</p>
  
<h2>Grouped options</h2>
<p>
  <label for="fruit_4">What’s your favorite fruit?</label>
  <select name="fruit_4" id="fruit_4">
    <optgroup label="Pome">
      <option>Apple</option>
      <option>Pear</option>
    </optgroup>
    <optgroup label="Citrus">
      <option>Orange</option>
      <option>Tangerine</option> 
    </optgroup>
  </select>
</p>
  
<h2>Required field</h2>
  <p>
    <label for="fruit_5">What’s your favorite fruit?</label>
  <select name="fruit_5" id="fruit_5" required aria-required="true">
    <option value="">-- Choose One --</option>
    <option>Apple</option>
    <option>Orange</option>
  </select>
</p>
  
<h2>Unsetting the appearance</h2>
  <p>
    <label for="fruit_6">What’s your favorite fruit?</label>
  <select name="fruit_6" id="fruit_6">
    <option value="">-- Choose One --</option>
    <option>Apple</option>
    <option>Orange</option>
  </select>
</p>
  
<h2>Custom CSS</h2>
  <p>
    <label for="fruit_7">What’s your favorite fruit?</label>
  <select name="fruit_7" id="fruit_7">
    <option value="">-- Choose One --</option>
    <option>Apple</option>
    <option>Orange</option>
  </select>
</p>
  
  <h2><code>select</code> with "other"</h2>
  <p>
    <label for="fruit_8">What’s your favorite fruit?</label>
<select name="fruit_8" id="fruit_8">
  <option value="">-- Choose One --</option>
  <option>Apple</option>
  <option>Orange</option>
  <option>Other</option>
</select>
<label for="fruit_8_other">If you chose "other," what <em>is</em> your favorite fruit?</label>
<input id="fruit_8_other" name="fruit_8">
  </p>

<h2>Radio field</h2>
  <fieldset>
  <legend>What’s your favorite fruit?</legend>
  <label>
    <input type="radio" name="fruit_9"
value="Apple">
    Apple
  </label>
  <label>
    <input type="radio" name="fruit_9"
value="Orange">
    Orange
  </label>
</fieldset>
  
<h2>Required radio</h2>
  <fieldset>
  <legend>Required fruit</legend>
  <label>
    <input type="radio" name="fruit_10" value="Apple" required>
    Apple
  </label>
  <label>
    <input type="radio" name="fruit_10" value="Orange" required>
    Orange
  </label>
</fieldset>
  
<h2>Radio with other</h2>
<fieldset>
  <legend>What’s your favorite fruit?</legend>
  <label>
    <input type="radio" name="fruit_11" value="Apple">
    Apple
  </label>
  <label>
    <input type="radio" name="fruit_11" value="Orange" checked>
    Orange
  </label>
  <label>
    <input type="radio" name="fruit_11" value="Other">
    Other
  </label>
  <p>
    <label for="fruit_11-other">If you chose "other," what <em>is</em> your favorite fruit?</label>
    <input id="fruit_11-other" name="fruit_11">
  </p>
</fieldset>
  
  <h2><code>datalist</code></h2>
  <p>
    <label for="fruit_12">What’s your favorite fruit?</label>
<input name="fruit_12" id="fruit_12" list="fruit_12-options">
<datalist id="fruit_12-options">
  <option>Apple</option>
  <option>Orange</option>
</datalist>
  </p>
  
  <button type="submit">See what you get</button>
</form>

<output></output>
</div>
</main>
!

CSS 

              
                body {
  margin: 0;
  padding: 1em;
}

div {
  display: grid;
}
@media (min-width: 60em) {
  div {
    grid-template-columns: 1fr 1fr;
  }
}

p {
  margin-bottom: 5em;
}

label {
  font-weight: bold;
  display: block;
  margin: .5em 0 .25em;
}

#fruit_6 {
  appearance: none;
}
#fruit_7 {
  background: green;
  color: white;
  font-family: "Comic Sans MS", "Comic Sans", cursive;
  font-size: 2rem;
}

fieldset {
  border: 0;
  margin: 0 0 5em;
  padding: 0;
}
legend {
  font-weight: bold;
}
label:has(input) {
  font-weight: normal;
}

output {
  display: block;
  border: 1px solid;
  background: #ebebeb;
  margin: 2em 0;
  padding: 1em;
  white-space: pre-wrap;
  height: 300px;
  overflow: scroll;
}
!

JS 

              
                var $output = document.querySelector("output"),
     $form = document.forms[0];

$form.addEventListener('submit',function(e){
  e.preventDefault();
  show("-- New form submission --");
  var form_data = new FormData($form);
  var data = [...form_data.entries()]
  var output = {};
  data.forEach(item => {
    output[item[0]] = item[1];
  });
  for ( key in output ) {
    show(`${key}: ${output[key]}`);
  }
  show("\r\n");
}, false);

function show(str) {
  $output.innerText += str + "\r\n";
}
!
999px

Console