Animating in other Units

The YUI Animation Utility allows you to animate style attributes in any CSS unit.

For this example, we will animate the width of the <div> element named demo in EM units. Using EMs is nice, because it becomes relative to the text size, and will scale as the user changes the browser text size setting.

Add a little style so that we can see the animation in action:

<style type="text/css"> #demo { background:#ccc; width:30em; } </style>

Create the demo element and a button to run the animation:

<div id="demo">Demo</div> <button id="demo-run">run</button>

Now we create an instance of YAHOO.util.Anim, passing it the element we wish to animate, and the style attribute(s) to be animated. Because we are changing the unit to something other than the default ("px"), the from field is required:

<script type="text/javascript"> var attributes = { width: { from: 30, to: 10, unit:'em' } }; var anim = new YAHOO.util.Anim('demo', attributes); </script>

The final step is to call the animate method on our instance to start the animation. To keep things simple, we will animate when the document is clicked:

<script type="text/javascript"> YAHOO.util.Event.on('demo-run', 'click', function() { anim.animate(); }); </script>

This is an example of animating in units other than pixels.

Configuration for This Example

You can load the necessary JavaScript and CSS for this example from Yahoo's servers. Click here to load the YUI Dependency Configurator with all of this example's dependencies preconfigured.