How to return a C++ Class to NODE.JS

I think, as described in Napi::Object docs, you cannot instantiate an object with a custom class. Only primitive values. Therefore I would suggest creating an empty Napi::Object and using it's Set to map the values.

Napi::Object ret = Napi::Object::New(env);

ret.Set("my_float", Napi::Number::New(env, (float)tmp.my_float()));

Fill all the fields and return the object. Just like you did with the exports

You can fit a custom class inside Napi::Object, it is convenient for destruction:

class MyObject : public Napi::ObjectWrap<MyObject> {
  void * inner_obj_;
}

And use reinterpret_cast to call it:

reinterpret_cast<MyClass *>(inner_obj_)->my_float();