I contribute to NodeGui, Qt on Nodejs. It doesn't try to emulate the C++ API by allowing subclassing. Instead it exposes most methods on QWidget classes/subclasses which process QEvent objects (and their subclasses) in the form of events which you can subscribe to as an application. You can listen to signals and also QEvent related traffic in much the same way. So, if you want to subclass a QWidget to do your own custom rendering/painting, you would create an instance of QWidget and then listen to/hook into, the incoming requests to repaint. Qt sees a normal QWidget instance, but you can customise it do act like the subclass you desire. This avoids any attempt to do a real C++ subclass at runtime. Internally, NodeGui subclasses almost every QWidget (and more) to hook into them to allow this. This works far better than you might expect and saves a ton of complexity.