Pen Settings

HTML

About HTML Preprocessors

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.

Learn more · Versions

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.

!
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.

Learn more · Versions

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).

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.

Powered by Algolia
About External Resources

You can apply CSS to your Pen from any stylesheet on the web. Just put a URL to it here and we'll apply it, in the order you have them, before the CSS in the Pen itself.

If the stylesheet 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 CSS 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.

Learn more

+ add another resource

JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient. For instance, CoffeeScript can help prevent easy-to-make mistakes and offer a cleaner syntax and Babel can bring ECMAScript 6 features to browsers that only support ECMAScript 5.

Learn more · Versions

Babel is required to process package imports. If you need a different preprocessor remove all packages first.

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.

Powered by Algolia
About External Resources

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.

Learn more

+ add another resource

Behavior

Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.

HTML 

              
                <link href="http://sparkx.online/secondary.css" rel="preload" as="style"/><!--not placed inside <HEAD> for purpose of this demo-->

<style id="critical">/*immediate cyan background by internal css*/
  body {background-color:cyan}
</style>

<div>
<h1>Triggering a Javascript/jQuery event after CSS has loaded .. AND RENDERED</h1><p>The above code presents a way to <b>remove critical CSS (&#x3C;style&#x3E; element) from HTML after being 100% sure, that external sheets have lazyloaded and rendered</b>.</p><p>This allows using universal, yet visually pleasing critical internal CSS globally over several projects.</p><p>Since some of the critical styles go visually against the lazyloaded ones,  so they need to be overridden (too much work), or removed. This is what happens with the second option:<ol><li>The document with critical internal CSS loads</li><li>Additional CSS is loaded after the document is rendered and interactive (good for SEO and UX)</li><li>Critical CSS is removed from HTML after the fancy additional <b>stylesheets have been loaded and truly rendered</b>.</li></ol><p>Using <i>setInterval();</i> to periodically check, whether a style, unique to secondary CSS, has truly been applied is a 100% working solution (may it be unpopular).</p><p>There are other solutions available, but only this one <b>prevents flickering which occured when the CSS is being manipulated</b> (lot of testing done on this). Check out more on this <a href="https://sparkx.online/triggering-javascript-jquery-after-css-has-loaded/" target="_blank">here</a> or alternatives in this   <a href="https://stackoverflow.com/questions/2571164/jquery-event-that-triggers-after-css-is-loaded/51267013" target="_blank">Stack Overflow post</a>.</p>

<p id="result">This paragraph will change to display loading time of external CSS.</p>
</div>

<!--loading jQuery-->
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>

<!--Changing "preload" to "stylesheet", to load external CSS. Wrapped in a 3 second setTimeout, to make the change visible -->
<script>
  setTimeout(function() {
$('*[rel="preload"]').attr("rel", "stylesheet");
    },3000); 
</script>

<!--Checking for CSS change, changing text of last <p>, when after it occurs. -->
<script> 
var i = 0;  
var CSSloadcheck = setInterval(function () {
  i++;
    if ($('body').css('opacity') != 1) {
    //when opacity is set to 0.99 by externatl sheet
	  $('style#critical').remove();
	  $('p#result').html('Critical CSS was removed after roughly ' + i*100 + "ms. Also, as a result, this paragraph changed and so did backround color - from cyan to orange.");
	  clearInterval(CSSloadcheck);  
      console.log(i);
  }
}, 100);
</script>
!

CSS
!

JS
!
999px

Console