The TypeScript programming language adds optional types to JavaScript, with support for interaction with existing JavaScript libraries via interface declarations. Such declarations have been written for hundreds of libraries, but they can be difficult to write and often contain errors, which may affect the type checking and misguide code completion for the application code in IDEs.

The rapid rise of JavaScript as one of the most popular programming languages of the present day has led to a demand for sophisticated IDE support similar to what is available for Java or C#. However, advanced tooling is hampered by the dynamic nature of the language, which makes any form of static analysis very difficult. We single out efficient call graph construction as a key problem to be solved in order to improve development tools for JavaScript. To address this problem, we present a scalable field-based flow analysis for constructing call graphs. Our evaluation on large real-world programs shows that the analysis, while in principle unsound, produces highly accurate call graphs in practice. Previous analyses do not scale to these programs, but our analysis handles them in a matter of seconds, thus proving its suitability for use in an interactive setting.

Modern IDEs support automated refactoring for many programming languages, but support for JavaScript is still primitive. To perform renaming, which is one of the fundamental refactorings, there is often no practical alternative to simple syntactic search-and-replace. Although more sophisticated alternatives have been developed, they are limited by whole-program assumptions and poor scalability.

Refactoring is a popular technique for improving the structure of existing programs while maintaining their behavior. For statically typed programming languages such as Java, a wide variety of refactorings have been described, and tool support for performing refactorings and ensuring their correctness is widely available in modern IDEs. For the JavaScript programming language, however, existing refactoring tools are less mature and often unable to ensure that program behavior is preserved. Refactoring algorithms that have been developed for statically typed languages are not applicable to JavaScript because of its dynamic nature. We propose a framework for specifying and implementing JavaScript refactorings based on pointer analysis. We describe novel refactorings motivated by best practice recommendations for JavaScript programming, and demonstrate how they can be described concisely in terms of queries provided by our framework. Experiments performed with a prototype implementation on a suite of existing applications show that our approach is well-suited for developing practical refactoring tools for JavaScript.