Array#bucket for JavaScript in ES6

array.bucket.js

Array.prototype.bucket = function(fn) {
  const results = [...Array(fn.length)].map(() => []);
  const buckets = results.map(bucket => bucket.push.bind(bucket));
  const noop = () => {};
  
  this.forEach(item => (fn.apply(item, buckets) || noop)(item));
  
  return results;
};

usage.js

const [even, odd] = [1,2,3,4,5,6].bucket(function(even, odd) { return this % 2 == 0 ? even : odd; });

const [fizz, buzz, fizzbuzz] = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15].bucket(function(fizz, buzz, fizzbuzz) {
  const [isFizz, isBuzz] = [this % 3 == 0, this % 5 == 0];
  if (isFizz && isBuzz) return fizzbuzz
  if (isFizz) return fizz;
  if (isBuzz) return buzz;
});