Animating Motion

The YUI Animation Utility allows you to animate the motion of an HTMLElement.

For this example, we will animate the position of a <div> element named demo. Note that you could accomplish this with a positioned element by animating offset properties ("top", "left", etc.), but those values are not necessarily in page coordinates. The points attribute, introduced in the YAHOO.util.Motion subclass, ensures that position is always relative to the document (unless using by rather than to, which is relative to the current position).

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

<style type="text/css"> #demo { background:#ccc; height:30px; width:30px; } </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.Motion, passing it the element we wish to animate, and the points attribute (an array of [x, y] positions), with the point we are animating to:

<script type="text/javascript"> var attributes = { points: { to: [600, 10] } }; var anim = new YAHOO.util.Motion('demo', attributes); </script>

The final step is to call the animate method on our instance to start the animation. The button will be the trigger that begins the animation sequence:

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

This is an example of animating the motion HTMLElement.