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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.

!
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-.

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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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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 

              
                <div class="container">
  <h1>More Fun With execCommand</h1>
  <p>Try it out by selecting some text in the paragraph below and the buttons:</p>
  
  <p contenteditable="true" spellcheck="false" class="box">
     Phasellus semper magna ac interdum scelerisque. Vestibulum laoreet sapien a nisi ullamcorper, nec luctus neque eleifend. Aliquam vel tortor justo. Nam aliquam dapibus mi ut volutpat. Donec eros turpis, gravida et neque nec, interdum pulvinar nibh. Ut vel sodales nulla, a tempus sem. Nunc facilisis pretium aliquam. Proin nulla ante, congue at purus sit amet, commodo placerat erat. Sed malesuada eros nulla, in cursus urna elementum finibus. Suspendisse posuere purus pellentesque rutrum tempor. Nunc nec tincidunt est. Sed convallis ligula quis dui laoreet maximus. Nulla pharetra placerat quam ut rutrum. Nullam sit amet vehicula nisi.
  </p>
  
  <p class="text-center">
    <button id="bold-btn">Bold</button>
    <button id="italic-btn">Italic</button>
    <button id="underline-btn">Underline</button>
    <button id="strike-through-btn">StrikeThrough</button>
  </p>

  <p class="text-center">
    <button id="supscript-btn">Supscript</button>
    <button id="superscript-btn">Superscript</button>
  </p>
  
   <p class="text-center">
    <button id="color-btn">Color</button>
    <button id="size-btn">Size</button>
    <button id="delete-btn">Delete</button>
    <button id="undo-btn">Undo</button>
    <button id="redo-btn">Redo</button>
  </p>
</div>
!

CSS 

              
                .box {
  border: 1px solid #aaa;
  border-radius: 4px;
  padding: 15px;
}

.text-center {
  text-align: center;
}
!

JS 

              
                document.addEventListener("DOMContentLoaded", () => {
  const $ = document.querySelector.bind(document);
  const boldBtn = $("#bold-btn"),
        italicBtn = $("#italic-btn"),
        underlineBtn = $("#underline-btn"),
        strikeThroughBtn = $("#strike-through-btn"),
        subscriptBtn = $("#supscript-btn"),
        superscriptBtn = $("#superscript-btn"),
        colorBtn = $("#color-btn"),
        sizeBtn = $("#size-btn"),
        deleteBtn = $("#delete-btn"),
        undoBtn = $("#undo-btn"),
        redoBtn = $("#redo-btn");
  
  boldBtn.addEventListener("click", () => {
    document.execCommand('bold');
  });
  
  italicBtn.addEventListener("click", () => {
    document.execCommand('italic');
  });
  
  underlineBtn.addEventListener("click", () => {
    document.execCommand('underline');
  });
  
  strikeThroughBtn.addEventListener("click", () => {
    document.execCommand('strikeThrough');
  });
  
  subscriptBtn.addEventListener("click", () => {
    document.execCommand('subscript');
  });
  
  superscriptBtn.addEventListener("click", () => {
    document.execCommand('superscript');
  });
  
  colorBtn.addEventListener("click", () => {
    document.execCommand('styleWithCSS', false, true);
    document.execCommand('foreColor', false, 'hotpink');
  });
  
  sizeBtn.addEventListener("click", () => {
    document.execCommand('styleWithCSS', false, true);
    document.execCommand('fontSize', false, '25px');
  });
  
  deleteBtn.addEventListener("click", () => {
    document.execCommand('delete');
  });
  
  undoBtn.addEventListener("click", () => {
    document.execCommand('undo');
  });
  
  redoBtn.addEventListener("click", () => {
    document.execCommand('redo');
  });
});

// https://developer.mozilla.org/en-US/docs/Web/API/Document/execCommand
!
999px

Console