When using ArchetypeLinkData, javascript objects, such as Map are not copied for new links, but rather shared. Is this the intended behaviour? Noticed it on GoJS 1.8.4.
GraphLinksModel.copyLinkData, just like Model.copyNodeData, only does a shallow copy of the given object. That means references will be shared. If you don’t want that, you can customize the copying by supplying a GraphLinksModel | GoJS API function.
Note that using a Map or a Set as a property value will mean that you cannot use Model.toJson or Model.fromJson. You will have to implement your own persistence mechanism.