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="banner" id="dynamicBanner">
<div class="banner-header" id="dynamicHeader">
<svg width="72" height="72" viewBox="0 0 72 72" xmlns="http://www.w3.org/2000/svg">
<path d="M25.5915 27.9395L31.6323 35.1616L31.8108 35.3749L32.0862 35.3358L41.4078 34.0109L36.406 41.9877L36.2582 42.2234L36.3805 42.4732L40.5212 50.9292L31.3891 48.6372L31.1193 48.5695L30.9195 48.763L24.1568 55.314L23.5148 45.9206L23.4958 45.6431L23.25 45.5129L14.9298 41.1056L23.6651 37.5922L23.9231 37.4884L23.971 37.2144L25.5915 27.9395Z" fill="currentColor" stroke="currentColor" />
<path d="M39.1961 15.5517L41.4513 18.2479L41.6298 18.4613L41.9052 18.4221L45.3853 17.9275L43.5179 20.9055L43.3701 21.1412L43.4925 21.391L45.0383 24.5479L41.629 23.6922L41.3592 23.6245L41.1594 23.8181L38.6347 26.2638L38.3949 22.7569L38.376 22.4794L38.1301 22.3492L35.024 20.7038L38.2851 19.3921L38.5432 19.2883L38.5911 19.0143L39.1961 15.5517Z" fill="currentColor" stroke="currentColor" />
<path d="M52.0745 34.8681L54.3297 37.5643L54.5082 37.7777L54.7836 37.7385L58.2637 37.2439L56.3963 40.2219L56.2485 40.4576L56.3709 40.7074L57.9167 43.8643L54.5074 43.0086L54.2376 42.9409L54.0378 43.1345L51.5131 45.5802L51.2734 42.0733L51.2544 41.7958L51.0086 41.6656L47.9024 40.0202L51.1635 38.7085L51.4216 38.6047L51.4695 38.3307L52.0745 34.8681Z" fill="currentColor" stroke="currentColor" />
</svg>
Respect for All
</div>
<div class="banner-body">
<span id="points">Shout Out! <b>2540 points</b></span>
</div>
</div>
<div class="color-picker-container">
<input type="color" id="colorPicker" value="#FFCF27">
<button onclick="updateColors()">Change Background</button>
</div>
body {
font-family: Arial, sans-serif;
margin: 0;
padding: 0;
display: flex;
flex-direction: column;
align-items: center;
justify-content: center;
align-items: center;
height: 100vh;
background-color: #f4f4f4;
}
.banner {
width: 100%;
max-width: 600px;
border-radius: 8px;
overflow: hidden;
padding: 32px;
box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
text-align: center;
font-size: 16px;
color: white;
background-color: #ffcf27; /* Default background */
transition: background-color 0.3s, color 0.3s;
}
.banner-header svg {
vertical-align: middle;
margin-bottom: 10px;
}
.banner-header {
display: flex;
flex-direction: column;
align-items: center;
justify-content: center;
align-items: center;
padding: 16px 0px 0px 0px;
font-size: 26px;
font-weight: bold;
}
.banner-body {
padding: 32px;
}
.color-picker-container {
margin-top: 16px;
text-align: center;
}
function luminance(r, g, b) {
var a = [r, g, b].map(function (v) {
v /= 255;
return v <= 0.03928 ? v / 12.92 : Math.pow((v + 0.055) / 1.055, 2.4);
});
return a[0] * 0.2126 + a[1] * 0.7152 + a[2] * 0.0722;
}
function contrastRatio(rgb1, rgb2) {
var lum1 = luminance(rgb1[0], rgb1[1], rgb1[2]);
var lum2 = luminance(rgb2[0], rgb2[1], rgb2[2]);
var brightest = Math.max(lum1, lum2);
var darkest = Math.min(lum1, lum2);
return (brightest + 0.05) / (darkest + 0.05);
}
function rgbToHsl(r, g, b){
r /= 255, g /= 255, b /= 255;
var max = Math.max(r, g, b), min = Math.min(r, g, b);
var h, s, l = (max + min) / 2;
if(max === min){
h = s = 0; // achromatic
} else {
var d = max - min;
s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
switch(max){
case r: h = (g - b) / d + (g < b ? 6 : 0); break;
case g: h = (b - r) / d + 2; break;
case b: h = (r - g) / d + 4; break;
}
h /= 6;
}
return [h, s, l];
}
function hslToRgb(h, s, l){
var r, g, b;
if(s === 0){
r = g = b = l; // achromatic
} else {
function hue2rgb(p, q, t){
if(t < 0) t += 1;
if(t > 1) t -= 1;
if(t < 1/6) return p + (q - p) * 6 * t;
if(t < 1/2) return q;
if(t < 2/3) return p + (q - p) * (2/3 - t) * 6;
return p;
}
var q = l <
0.5 ? l * (1 + s) : l + s - l * s;
var p = 2 * l - q;
r = hue2rgb(p, q, h + 1/3);
g = hue2rgb(p, q, h);
b = hue2rgb(p, q, h - 1/3);
}
return [Math.round(r * 255), Math.round(g * 255), Math.round(b * 255)];
}
function adjustColorLightness(r, g, b, amount){
var hsl = rgbToHsl(r, g, b);
hsl[2] += amount; // adjust lightness
hsl[2] = Math.min(1, Math.max(0, hsl[2])); // clamp between 0 and 1
return hslToRgb(hsl[0], hsl[1], hsl[2]);
}
function updateColors() {
var colorPicker = document.getElementById("colorPicker");
var banner = document.getElementById("dynamicBanner");
var header = document.getElementById("dynamicHeader");
var points = document.getElementById("points");
var bgColor = colorPicker.value;
banner.style.backgroundColor = bgColor;
var r = parseInt(bgColor.slice(1, 3), 16);
var g = parseInt(bgColor.slice(3, 5), 16);
var b = parseInt(bgColor.slice(5, 7), 16);
var lightened = adjustColorLightness(r, g, b, 0.9); // Lighten color by 90%
var darkened = adjustColorLightness(r, g, b, -0.45); // Darken color by 45%
var lightenedRgb = [lightened[0], lightened[1], lightened[2]];
var darkenedRgb = [darkened[0], darkened[1], darkened[2]];
var contrastWithLightened = contrastRatio([r, g, b], lightenedRgb);
var contrastWithDarkened = contrastRatio([r, g, b], darkenedRgb);
var textColor;
if (contrastWithLightened > contrastWithDarkened) {
textColor = `rgb(${lightenedRgb.join(",")})`;
} else {
textColor = `rgb(${darkenedRgb.join(",")})`;
}
header.style.color = textColor;
points.style.color = textColor;
}
window.onload = updateColors;
Also see: Tab Triggers