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CSS Base

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Add External Stylesheets/Pens

Any URL's added here will be added as <link>s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.

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Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

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Use npm Packages

We can make npm packages available for you to use in your JavaScript. We use webpack to prepare them and make them available to import. We'll also process your JavaScript with Babel.

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HTML Settings

Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

              <template id="myheadingtemplate">
    <i class="icon"></i>
    <a href="#" >#</a>
      i.icon:before {font-size:30px;}
      i.user:before {content: '☻';}
      i.pentagon:before {content: '⬟';}
      h1 {display: inline-block;}

<template id="myblocktemplate">
     div {
       border: 1px solid #000;
       padding: 5%;
       margin-bottom: 5%;

  <my-block heading-icon="user" heading="My important heading" >
    <div>Lorem ipsum</div>
    <!-- Notice how this does not get a border -->

  <my-block heading-icon="pentagon" heading="My second heading" >
    Lorem ipsum
              my-block div {
  color: green;

my-block my-block {
  color: red;
 * Create callback
 * @callback createElementCallback
 * @param {element} shaddow the shadow dom element
 * @param {scope} this the scope of the custom element

 * Generates a new component
 * @param {string} elementName Name of JavaScript Class for the element
 * @param {string} tagName Name of the tag produced (Must contain at least one '-')
 * @param {string} templateSelector Selector to template for the contents of the shadow DOM
 * @param {createElementCallback} postCreateCallback Callback triggered on construction of the element
function generateComponent(elementName, tagName, templateSelector, postCreateCallback) {

  //Create a custom element that extends from the base HTMLElement
  var elementPrototype = Object.create(HTMLElement.prototype);

  //On creation of an element this code triggers
  //Defines a shadow root within our custom element
  //Imports in the matching template
  //Triggers the callback for any further customisation
  elementPrototype.createdCallback = function() {
    var shadow = this.createShadowRoot();
    var template = document.querySelector(templateSelector);
    var clone = document.importNode(template.content, true);
    if (postCreateCallback) { postCreateCallback(shadow, this); }

  //Register the element name to the window
  window[elementName] = document.registerElement(tagName, {prototype: elementPrototype});

function slugify(slug) {
  return slug.toLowerCase().replace(/\s/g,'-');

generateComponent('MyBlockElement', 'my-block', '#myblocktemplate', function (shadow, scope) {
  var headingDOM = shadow.querySelector('my-heading');
  var heading = scope.getAttribute('heading');
  var icon = scope.getAttribute('heading-icon');
  if (headingDOM) {
    if (heading) {
      headingDOM.innerText = heading;
    } else { = 'none';
    if (icon) {
      headingDOM.setAttribute('icon', icon);

generateComponent('MyHeadingElement', 'my-heading', '#myheadingtemplate', function (shadow, scope) {
  var icon = scope.getAttribute('icon');
  var iconDOM = shadow.querySelector('i');
  var linkDOM = shadow.querySelector('a');
  if (icon && iconDOM) {
  if (linkDOM && scope.innerText !== '') {
      linkDOM.setAttribute('href', '#' + slugify(scope.innerText));

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