Filter ArrayCollection by index

Question

What is the syntax to reference the index in an ArrayCollection? I know if you remove  any filterFunction from an ArrayCollection it will be automatically ordered by index, but I want to explicitly refer to the index in a filterFunction:
private function filterUsingIndexNum(item:Object):Boolean{
                       if(item.index < someValue) return true;
                       else return false;     
// item.index is not referencing a property of the data in the ArrayCollection, I am actually trying to reference the index numder of the items in the ArrayCollection.
Thanks.

Answer 1

I just figured out the solution; actually, the correct syntax:
private function filterUsingIndexNum(item:Object):Boolean{
                       if(theArraCollection.getItemIndex(item) < someValue) return true;
                       else return false;