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