docs: function(callback, context)
    {
      var callbackContext = context || this;
  
      for (var i = 0; i < this.length; i++)
      {
        var item = this[ i ];
  
        callback.call( callbackContext, item, i );
  
        if ( this[ i ] !== item )
        {
          i--;
        }
      }
  
      return this;
    }