Creating n sized lists

creating-n-sized-lists.js

function last(xs){ return xs[xs.length - 1] }

function split(predicate, xs) {
  return reduce( xs
               , function(rv, x, i) { return predicate(x, i)?  rv.concat([[x]])
                                    :        /* otherwise */   (last(rv).push(x), rv) }
               , [[ ]]) }

function splitEvery(n, xs) { return split(function(x, i){ return i > 0 && i % n == 0 }, xs) }

usage.js

// reduce is Array.prototype.reduce.call.bind(Array.prototype.reduce)
reduce(list, intoTriplet, [])
reduce(list, intoTuple, [])