code: function pluck(obj, propertyName, recursive) {
      var results = [];
      this.preorder(obj, function(value, key) {
        if (!recursive && key == propertyName)
          return stopRecursion;
        if (_.has(value, propertyName))
          results[results.length] = value[propertyName];
      });
      return results;
    }
docs: Internal helper providing the implementation for `pluck` and `pluckRec`.