So that's why I sometimes see (function(){ /* stuff */ })(); being done! That's a far better idea than using global variables with naming conventions. I'm going to use function scopes instead. Obviously with nice clean names because I can get away with them now.
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Well, you could just "search all files" for your variable name, and if it doesn't turn up you should be fine.
But do you really need a global variable? If possible it's cleaner to wrap stuff in a function scope: