That's exactly why I used this specific example. I seen many code bases that use clone to avoid mutation problems so I wrote this specifically to show it can become a problem too.
I wrote a better article on globals. I plan on posting it next week
This seems more an issue with not understanding structuralClone, than one of understanding globals or lack thereof. There’s nothing wrong with the example, it does exactly what the code says it should — if you want counter to be “global” then structuralClone isn’t the function you want to call. The bug isn’t in how counter was in obj, the bug is in calling structuralClone when its behaviour wasn’t wanted.
With that said, it seems obvious that if you want to globally count the calls, then that count shouldn’t live in an argument where you (the function) don’t control its lifetime or how global it actually is. Simple has no say over what object obj.counter points to, it could trivially be a value type passed into that particular call, so if you know you want a global count then of course storing it in the argument is the wrong choice.
Global has two conflated meanings: global lifetime (ie lifetime of the whole program) and global access (which the article states). Simple needs global lifetime but not global access.
You rarely ”need” global access, although for things like a logger it can be convenient. Often you do need global lifetime.
I wrote a better article on globals. I plan on posting it next week