Earlier quoted context omitted.
Lua isn't usually associated with the functional languages. Besides mainly being promoted for embedded / extension use, I think the single biggest reason for this is that, while it has tail-call elimination, closures, first class functions, etc., you still have to say "return x" at the end of functions. I do a lot of FP-style stuff in Lua, and while the language doesn't actively resist it the way Python does, it's no…
you still have to say "return (val)" at the end of functions We have a bunch of code that compiles to both Common Lisp and Javascript, and those nasty "return" statements are one of the two biggest mismatches between the two languages (the other being Javascript's weird semantics around null, false, 0, and ""). One of these days I intend to try inserting them all automatically.
I've postponed learning Javascript until recently, because my work hasn't usually been web-oriented, but it's interesting how similar Javascript and Lua are. They seem to have been aimed at the same target, but for historical reasons Javascript's development got frozen early, while Lua had time to iron out many similar design flaws.
(In Lua, undefined and null are both nil, nil and false are "false-y", and everything else, including 0 and "", are truthy.)