Supporting Dynamic, Third-Party Code Customizations in JavaScript Using Aspects

Web sites and web browsers have recently evolved into platforms on top of which entire applications are delivered dynamically, mostly as JavaScript source code. This delivery format has sparked extremely enthusiastic efforts to customize both individual web sites and entire browsers in ways the original authors never expected or accommodated. Such customizations take the form of yet more script dynamically injected into the application, and the current idioms to do so exploit arcane JavaScript features and are extremely brittle. In this work, we accept the popularity of extensions and seek better linguistic mechanisms to support them. We suggest adding to JavaScript aspect-oriented features that allow straightforward and declarative ways for customization code to modify the targeted application. Compared to most prior aspect-related research, our work has a different motivation and a different target programming environment, both of which lead to novel design and implementation techniques. Our aspect weaving is entirely integrated into a new dynamic JIT compiler, which lets us properly handle advice to first-class functions in the presence of arbitrary aliasing, without resorting to whole-program code transformations. Our prototype demonstrates that an aspect-oriented approach to web-application customization is often more efficient than current idioms while simplifying the entire process.