They have the same options for renderers as legit fields. I use field JS field renderers all of the time on UI-only fields.

Sorry, I should be more clear. 

I am creating a field in Javascript and adding it to my model.

After i create the field I want to assign a field renderer in it . All done within Javascript. 

I was able to figure out a workaround. I define a custom snippet that applies to standard renderer.

When writing the XML for the field in a table, apply the custom snippet

Nice! I’ll remember that