Nodejs Utililty Methods Array Reduce

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

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

Array.prototype.reduce = function(f, firstValue){
   var value = firstValue;
   for (var i =0; i<this.length; i++){
      value = f(this[i], value);
   return value;
};
[1,2,3].reduce(function(currentValue ,value){return value+=currentValue;}, 0);
[1,2,3].reduce(function(currentValue ,value){return value*=currentValue;}, 0);
...

var arr = [0,1,2,3,4];
var sum = function(x, y) { return x + y; };
Array.prototype.reduce = function(f, inital) {
    var acc = initial;
    for (var i = 0; i < this.length; i++) {
        acc = f(acc, this[i]);
    return acc;
};
...

var arr = [0,1,2,3,4];
var sum = function(total, newValue) { return total + newValue; };
Array.prototype.reduce = function(f, initial) {
    var acc = initial;
    for (var i = 0; i < this.length; i++) {
        acc = f(acc, this[i]);
    return acc;
};
...

Array.prototype.reduce = function (f, value) { 
    for (var i = 0; i < this.length; i++) { 
        value = f(this[i], value)
    return value

Array.prototype.reduce = function (f, value) {
  for (var i = 0, len = this.length; i < len; i++) {
    value = f(this[i], value);
  return value;
};
var superheroes = ['superman', 'iron man', 'spiderman', 'batman'];
var totalLength = superheroes.reduce(function (elem, acc) {
  return elem.length + acc;
...

var data = [ 4, 8, 15, 16, 23, 42 ];
Array.prototype.reduce = function(f, value) {
    var i;
    for (i = 0; i < this.length; i += 1) {
        value = f(this[i], value);
    return value;
};
var add = function(a, b) {
...

var is_array_01 = function (value) {
  return value &&
    typeof value === 'object' &&
    value.constructor === Array;
};
var is_array = function (value) {
  return value &&
    typeof value === 'object'  &&
    typeof value.length === 'number'  &&
...

Array.prototype.reduce = function(f, value) {
    var i;
    for (i = 0; i < this.length; i += 1) {
        value = f(this[i], value);
    return value;
};
var data = [ 4, 8, 15, 16, 23, 42 ];
var add = function(a, b) {
...