Nodejs Utililty Methods Array Reduce

Array.prototype.reduce = function() {
  return this.length > 1 ? this : this[0];
};

var testArray1 = [1, 3, 5, 4, 2],
      sumArray = [];
Array.prototype.reduce = function() {
  var sum = 0;
    for (i=0;i<this.length; ++i) {
    sum += this[i];
      return sumArray.push(sum);
};
...

Array.prototype.reduce = function(aggregate, initial) {
  const len = this.length;
  let startIndex = 0;
  if(typeof initial === 'undefined') {
    initial = this[0];
    startIndex = 1;
  for(let i = startIndex; i < len; i += 1) {
    initial = aggregate(initial, this[i], i, this);
...

Array.prototype.reduce = function(callback, initial){
  initial = initial || 0;
  for (var i=0; i< this.length; i++) {
    initial = callback(initial, this[i], i, this);
  return  initial;
wat = [1,2, 3, 4]
console.log(wat);
...

Array.prototype.reduce = function(callback, initialValue) {
  var last, returned;
  this.forEach(function(item, index, array) {
    if (index == 0 && initialValue) {
      returned = initialValue;
    } else if (index == 1 && !initialValue) {
      returned = item;
    } else {
      last = returned, returned = null;
...

Array.prototype.reduce = function (callback, memo) {
    var obj = this;
    var value, accumulated_value = 0;
    for (var i = 0; i < obj.length; i++) {
        value = obj[i];
        accumulated_value = callback.call(null, accumulated_value, value);
    return accumulated_value;
};
...

Array.prototype.reduce = function(cb, res){
    var arr = Object(this);
    for(var i=0;i<arr.length;i++){
        res = cb.call(res, arr[i], i);
    return res;

Array.prototype.reduce = function (combiner, initialValue) {
  var counter,
    accumulatedValue;
  if (this.length === 0) {
    return this;
  else {
    if (arguments.length === 1) {
      counter = 1;
...

Array.prototype.reduce = function(combiner, initialValue) {
  var counter,
    accValue;
  if (this.length === 0) {
    return this;
  else {
    if (arguments.length === 1) {
      counter = 1;
...

Array.prototype.reduce = function(combiner, initialValue) {
  var counter,
    accumulatedValue;
  if (this.length === 0) {
    return this;
  else {
    if (arguments.length === 1) {
      counter = 1;
...