A recent trend in application development for the web is a move towards rich internet applications (RIAs). As more and more of the application logic is moved to the client, these applications can benefit from concurrency in order to increase overall performance as well as responsiveness of the application. Additionally, RIAs are often written in an event-driven style of programming to react to incoming events of a multitude of services that are integrated within the application.

In this paper we argue that, while individual technologies exist to tackle both concerns, these technologies cannot easily be integrated in an ad hoc way. In order to increase the modularisability and composability of RIAs we propose a new programming model based on actors and reactors that encapsulate different parts of the application. We show that our model is able to exploit some of the available concurrency while reducing the required amount of event-driven code. Both actors and reactors are modular components that can be glued together via a unified communication mechanism. We evaluate our approach by means of a motivating example of a collaborative code editor.