JS: Collection Transformations

[JohnMurray]

This is kind of getting into the realm of functional programming but is very common in idiomatic JS. The example should compare built-in as well as library based collection transformations. This includes functions such as map, flatMap, filter, each, etc. Ideally over multiple collection types. Since JS mainly has lists ([]) and maps ({}), we should focus on those types. I think we should stay away from the newer types in JS such as Map as they 1) aren't much used in typical JS code and 2) do not provide functional interfaces.

For the JS library section, Lodash should be used as it is 1) the gold standard and highly popular JS library and 2) provides a wide variety of collection-based methods.

For the C++ library section, I think Boost will likely be what is used, but am open to other suggestions as long as the library can be considered extremely mainstream and heavily used by the community at large.

[semmel]

@JohnMurray Good idea to keep it general too by leaving out Map and Set.
However there is an abstraction Iterator Protocol available for all those Array Object, Map, Set. It would be interesting to compare it with STL-Iterators. Of course there is no STL <algorithm> in JS - for that - yet again - a FP utility library is needed.

Regarding Lodash, I don't think it serves Functional Programming in JS best.
I enjoyed watching Hey Underscore, You're Doing It Wrong! to learn why

function square(n) {
  return n * n;
} 
_.map([4, 8], square);
// => [16, 64]

is not so good as haveing that arguments swapped

var squareAll = map(square);
squareAll([4, 8]); // -> [16, 64]

(Lodash's API is that of Underscore.js.)