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0 pointsinsin11y ago0 comments

NaN is passed to Array.prototype.join() as the separator to join strings with, so it gets coerced to String ("NaN"). It's deliberately working backward from the behaviour of Array.prototype.join() to create a contrived example for giggles, not a WTF.

It's no more a WTF than this, which follows the same principle: https://gist.github.com/insin/1183916

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moron4hire11y ago

Oh, I understand that. I was more trying to explain why someone might think it was a WTF.

And I'm pretty sure your example returns the decimal 15. Comma operator returns the last element in the list, and parseInt will truncate strings with non-number-like text to the number-like part. Here, the number-like part is a hexadecimal code, triggering another feature of parseInt that it can figure out the radix on the fly.

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