Hi all - I'm wondering if there is a better way to approach this than my current solution...

I have a list of items, I then retrieve another list of items. I need to compare the two lists and come up with a list of items that are existing (for update), a list that are not existing in the new list (for removal) and a list of items that are not existing in the old list (for adding).

Here is what I'm doing now - basically creating a lookup object for testing if an item exists. Thanks for any tips.

            for each (itm in _oldItems)
        {
            _oldLookup[itm.itemNumber] = itm;
        }

        // Loop through items and check if they already exist in the 'old' list
        for each (itm in _items)
        {
            // If an item exists in the old list - push it for update
            if (_oldLookup[itm.itemNumber])
            {
                _itemsToUpdate.push(itm);
            }
            else // otherwise push it into the items to add
            {
                _itemsToAdd.push(itm);
            }

            // remove it from the lookup list - this will leave only
            // items for removal remaining in the lookup
            delete _oldLookup[itm.itemNumber];
        }

        // The items remaining in the lookup object have neither been added or updated - 
        // so they must be for removal  - add to list for removal
        for each (itm in _oldLookup)
        {
            _itemsToRemove.push(itm);
        }