As far as I understand JS code is being run natively in the browser. Node has been hooked to the native engine, so V8 is not involved.

At LeaningTech we have since several months been able to run nodejs, but also python and ruby using our Wasm based x86 VM (CheerpX), the demo is available here: https://repl.leaningtech.com/?nodejs

With our solution the full Linux x86 binary of nodejs is running including the whole of V8 and its JIT engine. Of course fully client side.