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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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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

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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 

              
                <h1>Dialog with Popover Demo</h1>
<p>
  The following button opens a modal dialog containing buttons that open manual popovers. The first popover can't be interacted with, it's broken. The second one is fine, you can activate its button. Can you tell the difference?
</p>
<button id="open-dialog-btn" type="button">
  Open Dialog
</button>
<dialog id="fancy-dialog">
  <section>
    <h2>Interesting Stuff</h2>
    <p>Here are some interesting details about this awesome item! Wanna add it as a favorite?</p>
      <button class="red-btn" type="button" popovertarget="outer-popover">
        Save as favorite (broken)
      </button>
      <button class="green-btn" type="button" popovertarget="inner-popover">
        Save as favorite (interactive)
      </button>
    <p>This is another paragraph.</p>
    <div>
      <button id="close-dialog-btn" type="button">
        Close Dialog
      </button>
    </div>
    <div id="inner-popover" popover="manual" role="alert">
      Item was saved as a favorite. Click the button if you want to. 😊
      <button type="button" popovertarget="inner-popover">
        Undo
      </button>
    </div>
  </section>
</dialog>
<div id="outer-popover" popover="manual" role="alert">
  Item was saved as a favorite. Try clicking the button and weep! 😿
  <button type="button" popovertarget="inner-popover">
    Undo
  </button>
</div>
!

CSS 

              
                html {
  font-family: sans-serif;
}

button {
  background: lighgray;
  font-size: 1rem;
  padding: 0.5rem 1rem;
  
  &.red-btn {
    background: #fa7a6f;
  }
  &.green-btn {
    background: #cfe5cc;
  }
}

dialog {
  border: none;
  box-shadow: 0px 3px 3px -2px rgba(0, 0, 0, .2), 0px 3px 4px 0px rgba(0, 0, 0, .14), 0px 1px 8px 0px rgba(0, 0, 0, .12);
  padding: 0;
  
  section {
    padding: 1rem;
  }

  h2 {
    margin: 0;
  }
}

[popover] {
  background: darkred;
  border: none;
  border-radius: 0.25rem;
  box-shadow: 0px 3px 3px -2px rgba(0, 0, 0, .2), 0px 3px 4px 0px rgba(0, 0, 0, .14), 0px 1px 8px 0px rgba(0, 0, 0, .12);
  color: white;
  font-size: 1rem;
  inset: auto 0.5rem 0.5rem 0.5rem;
  margin: 0 auto;
  padding: 0.5rem;
  
  &#inner-popover {
    background: darkgreen;
  }
}
!

JS 

              
                const openDialogBtnRef = document.getElementById("open-dialog-btn");
const closeDialogBtnRef = document.getElementById("close-dialog-btn");
const dialogElementRef = document.getElementById("fancy-dialog");
const innerPopoverRef = document.getElementById("inner-popover");
const outerPopoverRef = document.getElementById("outer-popover");

openDialogBtnRef.addEventListener("click", openMyDialog);
closeDialogBtnRef.addEventListener("click", closeMyDialog);
dialogElementRef.addEventListener("close", onDialogClose);

function openMyDialog() {
    dialogElementRef.showModal();
}
function closeMyDialog() {
    dialogElementRef.close();
}
function onDialogClose() {
  innerPopoverRef.hidePopover();
  outerPopoverRef.hidePopover();
}
!
999px

Console