Nodejs Utililty Methods Number Value Check

Number.prototype.isEven = function(){
  return this % 2 === 0;

Number.prototype.isEven = function (){
  return this.isOdd() == false;

Number.prototype.isEven = function () { return (this % 2) === 0; }; 
Number.prototype.isOdd = function () { return Math.abs(this % 2) === 1; };
Array.prototype.isEmpty = function () { return this.length === 0; };
Array.prototype.hasItem = function (item) { return this.indexOf(item) >= 0; };
Array.prototype.remove = function (item) {
  var index = this.indexOf(item);
  if (index >= 0)
    this.splice(index, 1);
};
...

Number.prototype.isEven = function () {
    if (this % 2 === 0) {
        return true;
    } else return false;
};
function sumFibs(num) {
    var sumFibArr;
    var fibArray = fibArrayGenerator(num);
    fibArray = fibArray.filter(function (value) {
...

window.log = console.log;
function fib(num) {
  return (num < 3) ? num : fib(num - 1) + fib(num - 2);
Number.prototype.isEven = function() {
  return (this % 2 === 0) ? true : false;
};
function fibSum() {
  var i = 1,
...

Number.prototype.isEven = function() {
    return !(this % 2);

Number.prototype.isOdd = function () {
  return new Boolean(this.valueOf()&1);

function isOdd(num) {
  if (typeof num === 'number') {  
    return ((num % 2) === 1) || ((num % 2) === -1) ? true : false;
  else {
    throw 'Not a number';
console.log(isOdd(3)); 
...

Number.prototype.isOdd = function() {
    return !!(this % 2);

Number.prototype.odd = function () {
  return (this % 2 == 1)