I'm guessing map, filter, fold, reduce etc were born from adopting functional programming methods. Sounds like you're not really into that style (while I totally agree about lack of side effects and mutation). It sounds kind of weak, but I would say to truly get to the heart of your question, work with some Haskell or purescript (or look into lambda calculus), instead of trying to compare JavaScript code.
I'm guessing map, filter, fold, reduce etc were born from adopting functional programming methods. Sounds like you're not really into that style (while I totally agree about lack of side effects and mutation). It sounds kind of weak, but I would say to truly get to the heart of your question, work with some Haskell or purescript (or look into lambda calculus), instead of trying to compare JavaScript code.
Maybe ReasonML could help too, because it's closer to JavaScript.