i suppose the solution must be more native and contain basic language feature.))

I remember what functions exist in many languages, then do a search to find out what that particular language calls them. Most languages have a similar set of basic functions (except those languages that don't support higher-order functions cough), and that set really isn't very big. Most of what ZozoFouchtra lists exist under some alias in all languages that can handle them. For example, I may search for “js fold” (knowing foldl and foldr from Haskell), which takes me directly to MDN's page about Array.prototype.reduce(). I don't use JS much, but when I do, this is my workflow.

.forEach(), .every(), .filter(), .map(), .reduce() and .reduceRight() are (useful) methods of Array since JavaScript 1.6.
You'll find many occasions to use them in Codewars. ;)

see more @ https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array

How do you people come up with such answers ? do you google inbetween or you just know all the functions ?