My favourite would be Underscore.js – http://documentcloud.github.com/underscore/
I can’t guarantee this will work but I am 99% certain underscore has no reliance on the DOM so it should!
OK, I was focusing on the ECMAScript version; ECMAScript 5 introduces all the nifty Array methods. Need to pay more attention to what the different JScript levels support.
Since there is currently only one place in my code where Array.reduce() would have been really nice to have, I’ve simply written a plain-vanilla for loop instead. Nothing against added libraries, but time and place…
Oh, there it is. Right at the top. Last place I look for that sort of thing. C’est ma faute.
Later down I see we’re up to JS 1.8.5. Yummy. (Yes, I know, I used to be disdainful about the language. I still think automatic variable declaration is an absolutely execrable design decision, but there is a lot about the language to like.)