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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).

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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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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.

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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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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#filterList.container
  %div.filters
    %strong Filter:
    %ul.filter
      %li.filter__item
        %button.filter__button{"@click":"tag = ''", ":class":"{'filter__button--active': tag === ''}"} All
      - ['CSS', 'Animation', 'React'].each do |tag|
        %li.filter__item
          %button.filter__button{"@click":"tag = '" + tag+"'", ":class":"{'filter__button--active': tag === '"+tag+"'}"}= tag
    %p{"aria-live":"polite"} Showing {{ postCount }} posts tagged <em>{{ tag ? tag : 'all' }}</em>
        

  %div.posts
    - [{title: 'Are There Random Numbers in CSS?',
    excerpt: 'CSS allows you to create dynamic layouts and interfaces on the web, but as a language, it is static: once a value is set, it cannot be changed.',
    tags: ['CSS', 'Animation']},
    {title: 'Working with Framer Motion',
    excerpt: 'Matt Perry from Framer and I take a look at the React animation library Framer Motion. First, we take a look at how simple the API is.',
    tags: ['Animation', 'React']},
    {title: 'Digging Into the Preview Loading Animation in WordPress',
    excerpt: 'WordPress shipped the Block Editor (aka Gutenberg) back in version 5.0 and with it came a snazzy new post preview screen that shows the WordPress logo drawing itself while the preview loads.',
    tags: ['Animation']},
    {title: 'Grid, content re-ordering and accessibility',
    excerpt: 'Take this: That HTML ends up in the DOM that way (and thus how it is is exposed to assistive technology), and by default, those list items are also visually shown in that order. ',
    tags: ['CSS', 'Accessibility']},
    {title: 'Revisiting prefers-reduced-motion, the reduced motion media query',
    excerpt: 'Two years ago, I wrote about prefers-reduced-motion, a media query introduced into Safari 10.1 to help people with vestibular and seizure disorders use the web.',
    tags: ['Animation', 'Accessibility']},
    {title: 'Tabs: It’s Complicated',
    excerpt: 'I’ve said before one quick and powerful thing you can learn as a front-end developer just getting starting with JavaScript is changing classes.',
    tags: ['Accessibility', 'React']},
    {title: 'The Dark Side of the Grid',
    excerpt: 'Manuel Matuzovic makes the point that in order to use CSS grid in some fairly simple markup scenarios, we might be tempted to flatten our HTML ',
    tags: ['Accessibility', 'CSS']}].each do |post|
      %article.post{ "v-if":post[:tags].to_json + ".includes(tag) || tag === ''"}
        %header.post__header
          %h2= post[:title]
        %p= post[:excerpt]
        %footer.post__footer
          %span= "Tagged: " + post[:tags].join(", ")
!

CSS 

              
                /* RGB */
$white: #FDFDFF;
$primary: #3F5B69;
$primary--light: lighten($primary, 10%);
$primary--dark: #243B4A;
$secondary: #393D3F;

body {
  margin: 0;
  height: 100%;
  display: flex;
}

.container {
  font-size: 20px;
  color: $white;
  background: $primary--dark;
  background: linear-gradient(225deg, $primary--dark 0%, $primary 50%) no-repeat;
  padding: 1em;
  height: 100%;
}
.filter {
  display: flex;
  list-style-type: none;
  margin: 0;
  padding: 0;
}
.filter__item:not(:last-child) {
  margin-inline-end: .5rem;
}
.filter__button {
  border: 2px solid $white;
  background: none;
  color: $white;
  padding: .5rem;
  font-size: 1rem;
  
  &:hover, &:focus {
    background: $primary--dark;
    color: $white;
    cursor: pointer;
    outline: 0;
  }
  &--active, &--active:hover, &--active:focus {
    background: $primary--dark;
    border-color: $white;
    color: $white;
    cursor: default;
  }
}

.posts {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  width: 100%;
  margin: 1rem 0;
  padding: 0;
}
  
.post {
  padding: .5rem;
  margin: .5rem;
  color: $white;
  background: none;
  border: 2px solid $white;
  text-align: center;
  display: flex;
  flex-direction: column;
  
  &:hover, &:focus {
    background: $primary;
  }
}

.post__footer {
  margin-top: auto;
}
!

JS 

              
                 new Vue({
   el: '#filterList',
   data: {
     'tag': '',
     'postCount': ''
   },
   methods: {
     getCount: function(){
       let posts = this.$el.getElementsByTagName('article');
       return posts.length;
     }
   },
   beforeMount: function(){
     this.postCount = this.getCount();
   },
   updated: function(){
     this.postCount = this.getCount();
   }
});
!
999px

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