[tgv]

I don't care. The problem in this case is that if you install "isNumber", you use someone else's definition of what a number is. If you ever have to check if something is a number, you should do that according to your own specs, not hope someone else got it right. In this case, strings with all kinds of weirdness seem to be allowed, and perhaps that's not acceptable.

Only the fact that you can write a bunch of slightly different versions because of Javascript's flaws/features should be a sign that you just can't grab an arbitrary implementation and hope it matches your use case, and especially not if you don't/can't pin the version.