In https://github.com/microsoft/napajs/blob/master/docs/api/transport.md#transportable-types https://github.com/microsoft/napajs/blob/master/docs/api/tra... it

In https://github.com/microsoft/napajs/blob/master/docs/api/transport.md#transportable-types https://github.com/microsoft/napajs/blob/master/docs/api/tra... it sounds like there aren't completely isolated runtimes - "JavaScript standard built-in objects in the whitelist can be transported among napa workers transparently" and it seems to imply they are not transported via serialization but via a sharing mechanism leveraging multiple threads in the same runtime. (And also it talks about implementing your own Transportable classes)