gistfile1.js

var anim_hz = 30;


function AnimHandle(complete, callback)
{
	// No parameter ensures the handle represents a completed animation
	this.Complete = complete == null ? true : complete;
	this.Callback = callback;
}


function AnimateUpdate(handle)
{
	// Linear step the value and pass to the animation function
	handle.AnimFunc(handle.Value);
	handle.Value += handle.ValueInc;
	
	if (Math.abs(handle.Value - handle.End) > 0.01)
	{
    	window.setTimeout(handle.AnimUpdate, 1000 / anim_hz);
	}
	else
	{
		// Upon completion issue one final animation function call with the end value
		handle.AnimFunc(handle.End);
		handle.Complete = true;
	}
	
	if (handle.Callback)
		handle.Callback(handle.Complete);
}


function Animate(anim_func, start, end, time, callback)
{
    // Create a new animation handle
	var handle = new AnimHandle(false, callback);
	handle.Start = start;
	handle.End = end;
	handle.ValueInc = (end - start) / (time * anim_hz);
	handle.Value = start;
	
	// Cache the update function to prevent recreating the closure
	handle.AnimFunc = anim_func;
	handle.AnimUpdate = function() { AnimateUpdate(handle); };
	
	// Call for the start value
	handle.AnimUpdate();
	return handle;
}

/// USE


			this.AnimHandle = Animate(
				function (val) { item.ChildrenNode.style.height = val; },
				item.ChildrenNode.offsetHeight, 0, 0.2);