An Evaluation of Reactive Programming and Promises for Structuring Collaborative Web Applications

JavaScript programs are highly event-driven, resulting in 'asynchronous spaghetti' code that is difficult to maintain as the magnitude programs written in the language grows. To reduce the effects of this callback hell, various concepts have been employed by a number of JavaScript libraries and frameworks. In this paper we investigate the expressiveness of two such techniques, namely reactive extensions and promises. We have done this by means of a case study consisting of an online collaborative drawing editor. The editor supports advanced drawing features which we try to model using the aforementioned techniques. We then present a discussion on our overall experience in implementing the application using the two concepts. From this, we propose a roadmap of how to improve support of programming event-driven web applications in JavaScript.