How to keep cookie consistent across subdomains from same script?

[purijs]

I'm allowing a couple of website "example.com" and "example1.com" to use divolte scripts which are common for both of them.

Problem is, party_cookie set at "example.com" is different from "app.example.com". I know I can add the 'cookie_domain' param but since I'm allowing multiple website to consume the same script, I cannot hardcode the domain.

Is there some other alternative?