How to wait for effect queue completion?

[TTop]

I'd like to wait for an effect queue to be empty before proceeding
with code execution. How can I do this?

In this case, I'd like to fade out a div, modify it and then fade it
back in, but I don't want the modification to start until I know it's
completely faded out.

[TTop]

I should clarify... this is with scriptaculous.

[Thomas Fuchs]

You can use Effect.Event for this:

new Effect.Event({queue:'end',afterFinish:function(){
// your code
});