SP.Taxonomy.TermSetItem.owner property (sp.taxonomy)
Specifies the name of the protocol client user who is responsible for this TaxonomyItem object.
Applies to: apps for SharePoint | SharePoint Foundation 2013 | SharePoint Server 2013
var value = SP.Taxonomy.TermSetItem.get_owner()
SP.Taxonomy.TermSetItem.set_owner(a)