ValueTransformer

ValueTransformer is the template class to convert native types from and into JavaScript.

template <typename T, typename Enabled = void>
struct ValueTransformer {
  static std::optional<T> FromJS(Napi::Value);

  static Napi::Value ToJS(Napi::Env, const T &);
};

// There is also a helper function `ConvertToJS`
template <typename T>
Napi::Value ConvertToJS(Napi::Env env, T v);

All T which has a template specification of ValueTransformer<T>::FromJS could be treated as function arguments.
All T which has a template specification of ValueTransformer<T>::ToJS could be treated as function return value.