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.
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.
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.
The resource you are linking to is using the 'http' protocol, which may not work when the browser is using https.
CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.
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.
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).
Any URLs added here will be added as <link>
s in order, and before the CSS in the editor. You can use the CSS from another Pen by using its URL and the proper URL extension.
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.
You can also link to another Pen here (use the .css
URL Extension) and we'll pull the CSS from that Pen and include it. If it's using a matching preprocessor, use the appropriate URL Extension and we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency.
JavaScript preprocessors can help make authoring JavaScript easier and more convenient.
Babel includes JSX processing.
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.
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.
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.
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.
If you're using React / ReactDOM, make sure to turn on Babel for the JSX processing.
If active, Pens will autosave every 30 seconds after being saved once.
If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.
If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.
Visit your global Editor Settings.
<div class="ale" data-ale-type="diagonal" data-ale-src="https://crossorigin.me/https://zachsaucier.com/images/grapes.jpg"></div>
<div class="centered">
<h2>Asset loading effects</h2>
<p>For more loading effects, source code, and an article of how it works, check out <a href="https://github.com/ZachSaucier/Asset-Loading-Effects/tree/master">the GitHub page</a>.
</div>
$transDur: 0.5s;
.ale {
/* This sizes each asset element so that the width is 1.5 times bigger than the height.
If changed, the positioning some sub elements will need to be changed as
well. */
height:0;
padding-bottom:66%;
/* This part is for the effect itself */
background-size:cover;
position:relative;
overflow:hidden;
/* Add a default fade in for every effect */
&::after {
z-index:0;
content:'';
position:absolute;
top:0;
width:100%;
height:100%;
background-color:inherit;
}
&.complete::after {
opacity:0;
transition:$transDur * 2;
}
/* Make sure any SVG or ::before elements are above ::after elements */
> svg,
&::before {
z-index:1;
}
/* The diagonal loader */
&[data-ale-type="diagonal"] {
color:white;
/* Position the SVG loader diagonally */
> svg {
position:absolute;
top:50%;
width:125%;
-webkit-transform:translate(-10%, -50%) rotate(-33.333deg);
transform:translate(-10%, -50%) rotate(-33.333deg);
}
/* Create each half to be separated in the animation */
&::after,
&::before {
content:"";
width:125%;
height:100%;
position:absolute;
background:currentColor;
}
/* Position the left side */
&::before {
-webkit-transform-origin:bottom left;
transform-origin:bottom left;
-webkit-transform:rotate(-33.333deg);
transform:rotate(-33.333deg);
}
/* Position the right side */
&::after {
right:0;
-webkit-transform-origin:top right;
transform-origin:top right;
-webkit-transform:rotate(-33.333deg);
transform:rotate(-33.333deg);
}
/* Set the complete state for each part */
&.complete {
/* Fade out the SVG */
> svg {
transition:$transDur / 2;
opacity:0;
}
/* Slide out both sides */
&::before {
transition:$transDur * 2;
-webkit-transform:rotate(-33.333deg) translateY(-100%);
transform:rotate(-33.333deg) translateY(-100%);
}
&::after {
opacity:1;
transition:$transDur * 2;
-webkit-transform:rotate(-33.333deg) translateY(100%);
transform:rotate(-33.333deg) translateY(100%);
}
}
}
}
@import url(https://fonts.googleapis.com/css?family=Open+Sans);
body {
font-size:18px;
font-family: 'Open Sans', sans-serif;
}
.centered {
margin:0 auto;
max-width:900px;
box-sizing:border-box;
padding:20px;
}
// The elements that are the to be used for the asset
var assetElems = document.querySelectorAll(".ale"),
urlCreator = window.URL || window.webkitURL; // For URL creator usage later
// Add the asset loading effect for each element
[].forEach.call(assetElems, loadAsset);
// Load the asset in the way specified by the data attribute
function loadAsset(elem) {
// Determine which loader to create
var progressBarElem = getProgressBarElem(),
isVid = elem.getAttribute("data-ale-isVid") != undefined ? elem.getAttribute("data-ale-isVid") : false,
assetLoc = elem.getAttribute("data-ale-src");
// Load the asset via XHR so that we can track the progress
var req = new XMLHttpRequest();
// Attach the finished load listener
req.onload = loadFinished;
// Attach the progress listener
req.onprogress = loading;
// Actually make the request
req.open('GET', assetLoc, true);
req.responseType = 'blob'; // This must be after the open - FF can't handle do it before https://bugzilla.mozilla.org/show_bug.cgi?id=1110761
req.send();
// Determine which progress bar to use given the data attribute and return it
function getProgressBarElem() {
var type = elem.getAttribute("data-ale-type");
// Choose the progress bar type based on the lil-type
if(type !== "diagonal") {
console.log("A diagonal type was not given! Creating one anyway");
} else {
var line = new ProgressBar.Line(elem);
// Fix an IE issue
line.svg.setAttribute("preserveAspectRatio", "xMinYMid");
return line;
}
}
// Update the progress bar with the current value
function loading(evt) {
if (evt.lengthComputable) {
// ProgressBar.js animates using 0.0-1.0 as a range, so we need the progress in terms of that
progressBarElem.animate(evt.loaded / evt.total);
}
}
// Remove the loader when it's done and show the image
function loadFinished() {
// Currently, if it's not a video it's an image
if(!isVid) {
// Create a URL for the given response
var imgUrl = urlCreator.createObjectURL(req.response);
// Set that URL as the background of the element given
elem.style.backgroundImage = 'url(' + imgUrl + ')';
} else {
var video = document.createElement('video');
video.controls = true;
video.src = urlCreator.createObjectURL(req.response);
elem.appendChild(video); // Append the video since we can't do a background-video
}
// Finish the animation
progressBarElem.animate(1, function () {
// Add the "complete" class to show it's done
elem.classList.add("complete");
});
}
}
Also see: Tab Triggers