There is no generic “JavaScript runtime” interface that runtimes would implement, therefore support must be tailored to the specific interfaces of existing runtimes.

At one point we had UMD[0], which effectively provided runtime-agnostic interface, but ES modules were incompatible with that.

Deno and Bun have decent Node compatibility, so couldn't Node APIs be used as the generic runtime interface?

[0]: https://github.com/umdjs/umd