Unless you're completely impatient, you can pretty much take anybody with a "scripting" language background and throw them in and it's fine. Works the other way around, too. Python, Ruby, and Perl are all nearly the same language under the hood, with Javascript and Lua somewhat more distant but still not all that different. (Also, I mean someone who knows Javascript, not merely someone who can copy and paste some snippets of jQuery.)
Yeah, they may not know the exact APIs you're using, but that's usually the case anyhow.
What doesn't work so well, or at least takes a lot longer, is to take somebody with only Java, C/C++, or other such languages, and throw them in.
My old CTO would have argued with you that Perl was not a mere scripting language* and that our shop's style of coding was indeed object oriented. The other problem we ran into was that the programmers who loved other languages were very religious about it.
In fact I use to visualize that each programmer worshipped the specific animal that shown on the O'Reilly book cover: And I'm still haunted in my dreams by that camel. Of course the best programmers in my experience like to work in multiple languages -- but again there aren't that many of them...
* This was a few years ago so this was a reference to PHP and Cold Fusion which tended to get mashed into HTML. Python was around then, but a very new thing -- and this was before the age of Ruby on Rails.
"that our shop's style of coding was indeed object oriented"
All of the other languages I mentioned are roughly as OO as Perl. (You sometimes have to go looking for it, and Perl's probably ultimately the weakest at the core, but it's still there and mostly strong enough it doesn't matter.)
Well keep in mind that the above quote was made about twelve years ago. The problem that we had was that the people who would take up languages like PHP were what we'd call "script kiddies" who would copy and paste code and call themselves coders. Keep in mind that this was right before the bubble burst so there was a ton of BS going around too. Of course since that era I've seen programming languages mature -- and I've also seen the industry mature as well. Although i still see a great deal of BS... : D
Yeah, they may not know the exact APIs you're using, but that's usually the case anyhow.
What doesn't work so well, or at least takes a lot longer, is to take somebody with only Java, C/C++, or other such languages, and throw them in.