The index variable is declared outside of the callback and modified inside the callback

Oh I thought you meant _getTerminalObjectIndexById has a side effect. I wouldn't call .some setting some value outside it's callback a problem, it's basically the same thing as doing it with a for loop. Regardless, the code looks better with your changes so thanks slightly_smiling_face

It's a problem it you want to tree-shake the code and expect calls to some to be side-effect free