Because of the success in the Internet technologies, traditional applications such as drawing and spreadsheet software are now provided as web applications. These modern web applications adopt asynchronous programming that provides high responsive user interactions even if an application works without multi-threading. At the same time, as the scale of these applications becomes large, modular programming becomes important because it allows developers to separate concerns, meaning that the evolution of one module does not affect other modules. However, applying asynchronous and modular programming is difficult because asynchronous programming requires uncoupling of a module into two sub-modules, which are non-intuitively connected by a callback method. The separation of the module spurs the birth of other two issues: callback spaghetti and callback hell. Some proposals have been proposed without the lack of issues about modular programming. In this paper, we compare and evaluate these proposals applying them to a non-trivial open source application development. We then present a discussion on our experience in implementing the application using these proposals. Finally, we point out challenges that this kind of proposal should overcome toward a modular programming.