Dependence-driven delimited CPS transformation for JavaScript

Abstract

In today’s web applications asynchronous requests to remote services using callbacks or futures are omnipresent. The continuation of such a non-blocking task is represented as a callback function that will later be called with the result of the request. This style of programming where the remainder of a computation is captured in a continuation function is called continuation-passing style (CPS). This style of programming can quickly lead to a phenomenon called “call- back hell”, which has a negative impact on the maintain- ability of applications that employ this style. Several alter- natives to callbacks are therefore gaining traction within the web domain. For example, there are a number of frameworks that rely on automatically transforming sequential style code into the continuation-passing style. However, these frame- works often employ a conservative approach in which each function call is transformed into CPS. This conservative approach can sequentialise requests that could otherwise be run in parallel. So-called delimited continuations can remedy, but require special marks that have to be manually inserted in the code for marking the beginning and end of the continuation. In this paper we propose an alternative strategy in which we apply a delimited CPS transformation that operates on a Program Dependence Graph instead to find the limits of each continuation.We implement this strategy in JavaScript and demonstrate its applicability to various web programming scenarios.

Simpler Coordination of JavaScript Web Workers

“…In another experiment with our tools [20] (omitted from this paper to save space), we encountered several such distinguished background workers and already added support for them in our tool (the tool automatically generates code to make asynchronous API calls from our framework; the programmer does not need to write such boilerplate code her/himself). Further research is necessary, however, to study to what extent coordination languages can also be used to orchestrate asynchronous API calls as a solution to "callback hells", and whether there are advantages compared to existing approaches; see Philips et al [24].…”