Nodejs Utililty Methods Array Last Index

Array.prototype.lastIndexOf = function lastIndexOf(searchElement) {
  if (!(this instanceof Object)) {
    throw new TypeError(this + 'is not an object');
  var
  array = this,
  arrayIsString = array instanceof String,
  length = array.length,
  index = 1 in arguments ? Number(arguments[1]) || 0 : length - 1;
...

Array.prototype.lastIndexOf = function (e) {
    for (var i = this.length - 1, j; j = this[i]; i--) {
        if (j == e) { return i; }
    return -1;

Array.prototype.lastIndexOf = function(elem, from) {
  if (from == null) {
    from = this.length - 1;
  } else if (from < 0) {
    from = Math.max(0, this.length + from);
  for (var i = from; i >= 0; i--) {
    if (this[i] === elem) {
      return i;
...

Array.prototype.lastIndexOf = Array.prototype.lastIndexOf || function(elt )  {
    var len = this.length;
    var from = Number(arguments[1]);
    if (isNaN(from)) {
        from = len - 1;
    } else {
        from = (from < 0)
            ? Math.ceil(from)
            : Math.floor(from);
...

Array.prototype.lastIndexOf = function(item){
  var lastIndex = -1;
  for (var i=0; i<this.length; i++){
    if (this[i] === item){
      lastIndex = i;
  return lastIndex;

Array.prototype.lastIndexOf = function (o) {
    var index = this.length;
    for (; index >= 0; index--) {
        if (index in this && this[index] === o)
            return index;
    return -1;
};

Array.prototype.lastIndexOf = function(searchElement, fromIndex) {
  if (!fromIndex || !isFinite(fromIndex)) {
    fromIndex = this.length - 1;
  for (var i = fromIndex; i >= 0; --i) {
    if (this.hasOwnProperty(i) && this[i] === searchElement) {
      return i;
  return -1;

Array.prototype.lastIndexOf = function(v,b){
    var idx=-1;
  if(b===true && typeof(v)=="function"){
    for (var i=this.length-1;i>=0;i--) {
      if(v(this[i])){idx=i; break;}
  } else {
    for (var i=this.length-1;i>=0;i--) {
      if(this[i]===v){idx=i; break;}
...

Array.prototype.lastIndexOf = function(value, begin, strict)
  begin = +begin || 0;
  var i = this.length;
  while(i-- > begin)
    if(this[i] === value || strict && this[i] == value )
      return i;
...