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    If you monkey patch Array.prototype with negative indices, what’s the expected behavior of Array.prototype.indexOf? An index of -1 returned by that method means that the given item is not found in the array. You still have to have a way of representing the null case. But more importantly, -1 is so commonly understood to have this meaning that the benefits of breaking that behavior do not seem to justify the cost.

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      Not to mention the performance implications of bringing Proxy into the situation.