Base runtime code like URL, CommonJS can be shared. Even debugger support. Only difference is mainly the FFI, which is very different for Android and iOS/macOS. Shared runtimes codebase will make it easier to add more platforms as well. In future, maybe FFI code could be refactored to have a common interface which makes it easier to handle like native objects and their memory management across different FFI types (ObjC runtime, JNI).
Base runtime code like URL, CommonJS can be shared. Even debugger support. Only difference is mainly the FFI, which is very different for Android and iOS/macOS. Shared runtimes codebase will make it easier to add more platforms as well. In future, maybe FFI code could be refactored to have a common interface which makes it easier to handle like native objects and their memory management across different FFI types (ObjC runtime, JNI).