instanceof.cc

void doInstanceOf(napi_env env, napi_func_cb_info info) {
  napi_value arguments[2];
  napi_valuetype originalType, currentType, constructorPrototypeType;
  bool returnValue = false;
  napi_propertyname underunderProto;

  napi_get_cb_args(env, info, arguments, 2);

  if (napi_get_type_of_value(env, arguments[1]) != napi_function) {
    napi_throw_type_error(env, (char *)"constructor must be a function");
    return;
  }

  arguments[1] = napi_get_property(env, arguments[1],
    napi_property_name(env, "prototype"));
  constructorPrototypeType = napi_get_type_of_value(env, arguments[1]);

  if (constructorPrototypeType != napi_object) {
    napi_throw_type_error(env,
      (char *)"constructor prototype must be an object");
    return;
  }

  if (!napi_strict_equals(env, arguments[0], arguments[1])) {
    underunderProto = napi_property_name(env, "__proto__");

    for (originalType = currentType = napi_get_type_of_value(env, arguments[0]);
        !(currentType == napi_null || currentType == napi_undefined);
        arguments[0] =
          napi_get_property(env, arguments[0], underunderProto),
        currentType = napi_get_type_of_value(env, arguments[0])) {
      if (napi_strict_equals(env, arguments[0], arguments[1])) {
        returnValue =
          !(originalType == napi_number ||
            originalType == napi_boolean ||
            originalType == napi_string);
        break;
      }
    }
  }

  napi_set_return_value(env, info, napi_create_boolean(env, returnValue));
}