Here is an example of the original way:

import gs.TweenLite;
import gs.easing.*;
TweenLite.to(my_mc, 2, {x:300, y:100, ease:Elastic.easeOut, onComplete:myFunction});

And now the new/optional way to do it:

import gs.TweenLite;
import gs.utils.tween.TweenLiteVars;
import gs.easing.*;
var v:TweenLiteVars = new TweenLiteVars();
	v.addProps(x, 300, false, y, 100, true);
	v.ease = Elastic.easeOut;
	v.onComplete = myFunction;
TweenLite.to(my_mc, 2, v);


function myFunction(required:Number, ...optionalArgs):void
{
trace(required); // 1
trace(optionalArgs); // [2, 3, 4]
}
myFunction(1, 2, 3, 4);


The same functionality can be achieved a couple other ways. This next example you set a default value for each variables you pass. But this isn’t an undetermined number of arguments.


function myFunction(option1:Number=0, option2:Number=null):void
{
trace(option1); // 1
trace(option2); // null
}
myFunction(1);


Another way is similar to the way jQuery does it plugins. I don’t have an example of it but you pass all of your variables that you want in an object to the function. You can have any number of items in the object. Inside the function you have default values in case the variables aren’t passed. Then the variables that were passed overwrite the default values.

[Updated July 28, 2008] Here is an example of an Actionscript classes bases example.