Function as

system/include/emscripten/val.h:520–524

  template<typename T, typename ...Policies>
  T as(Policies...) const {
    using namespace internal;

    return internalCallWithPolicy<EM_INVOKER_KIND::CAST, WithPolicies<Policies...>, T>(as_handle(), nullptr, *this);
  }

// Prefer calling val::typeOf() over val::typeof(), since this form works in both C++11 and GNU++11 build modes. "typeof" is a reserved word in GNU++11 extensions.
  val typeOf() const {