Nodejs Utililty Methods Array Object Key

Array.prototype.addIfUnique = function(key, value)
  if(this.contains(key))
    this[key] = value;
  else
    this.push(key);
    this[key] = value;

Array.prototype.by = function( key, id )
  var index = this.length;
  while( index-- )
    if( this[ index ][ key ] == id ) {
      return this[ index ];
};

Array.prototype.changeItem = function( key, property, value )
  var done = false;
    for(var i = 0; i < this.length; i++)
        if( this[i]["id"] == key)
          this[i][property] = value ; done = true;
    return done;
};

Array.prototype.containsProp = function(key,str) {
  var i = this.length,
    holder = [];
  while (i--) {
    if (this[i][key] === str) {
      holder.push(this[i]);
  return holder;
...

Array.prototype.containsReturn = function(key, value) {
    var i = this.length;
    while (i--) {
        if (this[i][key] === value){
            return i;
    return false;

Array.prototype.getKeys = function(){
  var keys = '';
  for(var i in this) keys += ',' + i;
  return keys.substr(1).split(',');

Array.prototype.hasKey = function(){ 
  for(i in this){ 
    if(i === arguments[0]) 
      return true; 
  }; 
  return false; 
};

Array.prototype.hasMultipleByKey = function(key) {
    var foundOnce = false;
    var i = this.length - 1;
    while (i >= 0) {
        if (this[i].getKey() === key) {
            if (foundOnce)
                return true;
            else
                foundOnce = true;
...

Array.prototype.keys = function keys () {
  return new ArrayIterator(this, 'key');
};

Array.prototype.notIn = function( key, array )
    return this.filter( function(element)
        var flag = true;
        for(var i = 0; i < array.length; i++)
            if( element[key] == array[i][key]) flag = false;
        return flag;
    });
};