Flatten on Array.prototype

Array.prototype.flatten

// Flattens nested arrays down to one
// ex. [[1,[2,[3,4]]],5,[6],[[[7]]]] => [1,2,3,4,5,6,7]
Array.prototype.flatten = function flatten() {
  return this.reduce(function(acc, item) {
    if (Array.isArray(item) && item.some(Array.isArray)) {
      return acc.concat(item.flatten());
    }
    return acc.concat(item);
  }, []);
};