SP.Publishing.VariationLabel.isSource property (sp.publishing)
Determines whether the VariationLabel is set as the source label.
Applies to: apps for SharePoint | SharePoint Foundation 2013 | SharePoint Server 2013
var value = SP.Publishing.VariationLabel.get_isSource()
Remarks
Returns true if the VariationLabel is a source label; otherwise, false. A source label represents the site or pages that are the source of authoring and publishing and are used to copy changes to target variation sites.