Nodejs Utililty Methods Array Append Item

Array.prototype.add = function(index, element) {
  if (arguments.length == 2) {
    this.splice(index, 0, element);
  } else {
    this.push(index);
};

Array.prototype.add = function(index, item){
  if (item === undefined){
    item = index;
    index = 0;
  while (index > this.length){
    this.push(undefined);
  this.splice(index, 0, item);
...

var SEP = ',';
Array.prototype.add = function(item) {
    for ( var i = 0; i < this.length; i++) {
        if (this[i] === item) {
            return this;
    this[this.length] = item;
    return this;
...

Array.prototype.add = function (obj) {
    var i = this.length;
    this[i] = obj;
    return i;
};

Array.prototype.add = function(other) {
    console.assert(this.length == other.length, 'add: len(a) != len(b)');
    var ret = new Array(this.length);
    for(var i = 0; i < ret.length; i++)
        ret[i] = this[i] + other[i];
    return ret;

"use strict";
Array.prototype.add = function(value) {
    this.push(value);