Returns the result of applying concat to the result of applying a function to values.
npm i -S mapconcat
var assert = require('assert');
var mapconcat = require('mapconcat');
function reverse(arr) {
return arr.reduce(function(acc, val, idx) {
return acc.concat(arr[arr.length - idx - 1]);
}, []);
}
var a = [3, 2, 1];
var b = [6, 5, 4];
var arr = mapconcat([a, b], reverse);
assert.deepEqual(arr, [1, 2, 3, 4, 5, 6]); // true