Nodejs Utililty Methods Number Iterate

"use strict";
Number.prototype.__iterator__ = function (iterKeys) {
  if (this % 1) {
    throw new TypeError("Integer expected for number iterator");
  var i = 1 - iterKeys,
      j = this + i;
  if (j < 0) {
    i = j - i + iterKeys;
...

Number.prototype.downto = function (down, iterator) {
  for (var i = this.valueOf(); i >= down; i--) {
    iterator(i);
  return this.valueOf();
};

Number.prototype.iters = function () {
    return [(this for (x of [0])),
            (this for (y of [0]))];
};
var [a, b] = (3).iters();
var three = a.next();
assertEq(Object.prototype.toString.call(three), '[object Number]');
assertEq(+three, 3);
assertEq(b.next(), three);
...

Number.prototype.upto = function (up, iterator) {
  for (var i = this.valueOf(); i <= up; i++) {
    iterator(i);
  return this.valueOf();
};

Number.prototype.upto = function (from) {
  var a = [];
  var to = this.valueOf();
  var i = to - 1;
  while (i++ < from) {
    a.push(i);
  return a;
};
...

Number.prototype.upto = function (t, cb) {
  var i = this;
  if(t < this) {
    return +this;
  while (i <= t) {
    cb(i++);
  return +this;
...

Number.prototype.upto = function(t, cb) {
  var i = this;
  if(t < this) return +this;
  while (i <= t) { cb(i++); }
  return +this;
};

Number.prototype.downto = function (t, cb) {
  var i = this;
  if(t > this) {
    return +this;
  while (i >= t) {
    cb(i--);
  return +this;
...

Number.prototype.downto = function(t, cb) {
  var i = this;
  if(t > this) return +this;
  while (i >= t) { cb(i--); }
  return +this;
};

Number.prototype.downto = function (to) {
  var a = [];
  var from = this.valueOf();
  var i = from + 1;
  while (i-- > to) {
    a.push(i);
  return a;
};
...