Because it's a supremely bad habit to get into. You really shouldn't be concatenating integers and strings, even if the poorly-designed language lets you do it. Quick: what's the correct result of "3" + 5? Is it 8, or "35"? Javascript gives you one answer, PHP gives you another, and sensible languages like Python, Haskell, etc. give you the only correct answer: an error.

This is a fundamental part of the language - then why shouldn't you takle advantage of it? Everyone with a fair amount of knowledge of JS know how this works.

This solution adds integers and strings, which is never a good idea. Instead of 0+r, 0+g and 0+b, it would have been better to write "0"+r, "0"+g, and "0"+b.

Indeed.

That's just overkill.

You're right about self.

It's more of a reflex than a real will.

For the prototype part. Indeed... my bad.

Oh ! Right, I missed that.

Thank you for your answer.

Hi, I'm not that good with regexp,

but can anyone explain to me why this one doesn't work :

/^(((1|2)?[0-9]?[0-9])\.){3}((1|2)?[0-9]?[0-9])$/

Which IP wouldn't work for example?