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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

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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.

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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 class="wrap">
   <h2>JavaScript unwrap children</h2>
   <p>Remove green parent div and leave child divs in page.</p>
   <p>A JavaScript substitute for <code>display:contents;</code> in all browsers.<br>How can this script be run with a media query or based on screen widths?</p>
   <p><b>Reduce Browser Window to kick in media query</b><br> Firefox 56+ will use <code>display:contents;</code>.</p>
   <div class="sidebar remove">
      <div class="child">child div to remain in page</div>
      <div class="child">child div to remain in page</div>
      <div class="child">child div to remain in page</div>
   </div>
</div>
!

CSS 

              
                /* check for display:contents support */
detect {
	display:none
}
@supports ( display: contents ) {
 detect {
	display:block;
	}
}


.wrap {
   width:90%;
   max-width:1000px;
   margin:auto;
   padding:20px;
   outline:1px solid red;
   box-sizing: border-box;
}
.sidebar {
   margin:10px 0;
   padding:40px;
   background:lime;
}
.child {
   background:#eee;
   margin:10px 0;
   padding:10px;
}
@media all and (max-width: 760px) {
   .remove {
      display:contents;
   }
}
!

JS 

              
                (function() {
    // detect CSS display:contents support by checking elements display as it is set to block in css supports rule
    var newEl = document.createElement("detect");
    document.body.appendChild(newEl);

    if (getComputedStyle(newEl).getPropertyValue("display") === "none") {

        //first save html so we can re-instate it
        var oldHtml = document.querySelector('.sidebar').cloneNode(true);

        function unwrap(sidebar) {
            oldHtml = document.querySelector('.sidebar').cloneNode(true);
            // place childNodes in document fragment
            var docFrag = document.createDocumentFragment();
            while (sidebar.firstChild) {
                var child = sidebar.removeChild(sidebar.firstChild);
                docFrag.appendChild(child);
            }
            // replace sidebar with document fragment
            sidebar.parentNode.replaceChild(docFrag, sidebar);
        }

        function wrap(child, parent, children) {
            parent.insertBefore(oldHtml, child, children);
            var i;
            for (i = 0; i < children.length; ++i) {
                children[i].remove();
            }
        }


        var mql = window.matchMedia("screen and (max-width: 760px)")
        mediaqueryresponse(mql) // call listener function explicitly at run time
        mql.addListener(mediaqueryresponse) // attach listener function to listen in on state changes

        function mediaqueryresponse(mql) {
            if (mql.matches) {
                unwrap(document.querySelector('.sidebar'));
            } else {
                if (document.querySelector('.sidebar')) return;

                wrap(document.querySelector('.child'), document.querySelector('.wrap'), document.querySelectorAll('.child'));
            }
        }

    }

})();
!
999px

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