Detect Pseudo-Element Animation Support

By  on  

A while back I posted an interesting tidbit from Daniel Buchner which allows developers to detect DOM node insertions with JavaScript and CSS animations; an awesome trick driven by CSS animations.  Lea Verou recently posted another detection snippet driven by CSS animations:  detecting pseudo-element animation support.  Here's how she did it!

The CSS

The test case can use any pseudo-element; in this case we'll use :before:

/**
 * Animation on pseudo-elements test
 */
@keyframes color { from,to { color: rgb(0, 255, 0); } }

.testElement:before {
	content: '(...testing animation support...)';
	color: rgb(255, 0, 0);
	animation: color 1s infinite;
	-webkit-animation: color 1s infinite;
}

A simple color animation is assigned to the pseudo-element and a spot-check of generated content will tell you if animation is supported (green) or not (red).  At the time of this post, only Firefox and Chrome support animation of psuedo-elements.

JavaScript Detection

Thanks to a tip from Ahmed El Gabri, I can present a method to detect pseudo-element animation:

var color = window.getComputedStyle(
	document.querySelector('.testElement'), ':before'
).getPropertyValue('color')

if(color == 'rgb(0, 255, 0)') {
	// Supported! :)
}

The same principal applies; if the color is green, the animation worked. A JavaScript method of feature detection makes everything better!

Unfortunately there doesn't appear to be a JavaScript method for testing generated content properties, so a spot check appears to be all we can rely on at this point.  Hopefully someone clever out there can figure out an efficient way to get the test result! Having a reliable method for detecting pseudo-element animation is excellent; another tool to add to the arsenal!

Recent Features

  • By
    JavaScript Promise API

    While synchronous code is easier to follow and debug, async is generally better for performance and flexibility. Why "hold up the show" when you can trigger numerous requests at once and then handle them when each is ready?  Promises are becoming a big part of the JavaScript world...

  • By
    Chris Coyier’s Favorite CodePen Demos

    David asked me if I'd be up for a guest post picking out some of my favorite Pens from CodePen. A daunting task! There are so many! I managed to pick a few though that have blown me away over the past few months. If you...

Incredible Demos

  • By
    Create Digg URLs Using PHP

    Digg recently came out with a sweet new feature that allows users to create Tiny Digg URLs which show a Digg banner at the top allowing easy access to vote for the article from the page. While I love visiting Digg every once in a...

  • By
    Web Audio API

    The Web Audio API allows developers to load and decode audio on demand using JavaScript.  The more I evaluate awesome games for Firefox OS TVs, the more I get to learn about these APIs that I normally wouldn't touch.  The following is a very basic introduction to the WebAudio API...

Discussion

  1. Actually, Chrome 26 added support for animating psuedo-elements, which was released to stable this week!

  2. I don’t know if this helps but I think you can check generated content properties, try this

    window.getComputedStyle(document.querySelector('.testElement'),':before').getPropertyValue('color'); 
    

    I read about it here http://adactio.com/journal/5429/

  3. Works like a champ in Chrome too!

    Maybe David needs an update ;)

  4. Updated my Chrome and I see green — yay!

  5. Didn’t IE (up to 10) not support the second argument in getComputedStyle() until recently? Did they fix it? I recall somebody reported it and they said it was by design (!).

  6. I have installed chrome online, but still it does not supporting Pseudo-Element. However, my Mozilla is showing green text …

  7. Rob Riggs

    What if I want to change the content property of the psuedo class, by keyframe? Any takers? Thanks!

  8. Greg Whitworth

    This works on IE internally (screenshot: http://imgur.com/9xc43rf). So in the next version of IE this will work :)

  9. Thanks for the tricks! I just wrote a isolate javascript file, if anyone’s interested.

    Tested on IE9, Chrome, QQ Mobile Browser.
    https://gist.github.com/chuyik/80af1383d215d4dff6fe

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!