Nodejs Utililty Methods Array Contain

"use strict";
Array.prototype.contains = function(value){
  var n = this.length
  for (var i = 0; i < n; i++){
    if (this[i] == value) return true
  return false

Array.prototype.contains = function(value) {
  return this.indexOf(value) !== -1;
};
Array.prototype.remove = function(value) {
  var index = this.indexOf(value);
  if ( index !== -1 ) {
    this.splice(index, 1);
};
...

Array.prototype.contains = function(value) {
  for(var i=0; i < this.length; i++) {
    if(this[i] === value)
          return true;
  return false;
};

Array.prototype.contains = function (what) {
  var contains = false;
  if (typeof what !== 'function') {
    this.forEach(function (item) {
      if (contains) return;
      contains = (item === what);
    });
    return contains;
  this.forEach(function (item) {
    if (contains) return;
    contains = what(item);
  });
  return contains;
};

Array.prototype.contains=function(x){
 for(i in this){
   if((x.city==this[i].city || x.firstName==this[i].firstname || x.lastName==this[i].lastname))
     return true;
 return false;

Array.prototype.contains = function (x) {
    return this.indexOf(x) > -1;
};

Array.prototype.containsAll = function(c) {
    for (var i = c.length - 1; i >= 0; i--) {
        if (!this.contains(c[i])) {
            return false;
    return true;
};

Array.prototype.containsAll = function(elements) {
  for (var i = 0; i < elements.length; i++) {
    if (!this.contains(elements[i])) {
      return false;
  return true;
};

Array.prototype.containsAll = function(items)
  for(var i = 0; i<items.length; i++) {
    if(this.indexOf(items[i]) == -1)
      return false;
  return true;
};

Array.prototype.containsAny = function(c) {
    for (var i = c.length - 1; i >= 0; i--) {
        if (this.contains(c[i])) {
            return true;
    return false;
};