Nodejs Utililty Methods Array Contain

Array.prototype.contains = function (element) {
   for (i in this)
       if (this[i] == element) return true;
   return false;

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

Array.prototype.contains = function(element) {
    var i = this.length;
    while(i--) {
        if (_.isEqual(this[i], element)) {
            return true;
    return false;

Array.prototype.contains = function(element) {
    return this.indexOf(element) != -1;
};
Object.prototype.toString = function() {
    try {
        return JSON.stringify(this);
    } catch(circular_structure) {
        return '[object Object]';
};

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

'use strict';
Array.prototype.contains = function (element) { 
  return (this.indexOf(element) !== -1); 
};

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

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

Array.prototype.contains = function(element) {
  return (-1 !== this.indexOf(element))

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