Exploring API Deprecation Evolution in JavaScript

Building an application using third-party libraries is a common practice in software development. As any other system, software libraries and their APIs evolve. To support version migration and ensure backward compatibility, a recommended practice during development is to deprecate API. Different from other popular programming languages such as Java and C#, JavaScript has no native support to deprecate API elements. However, several strategies are commonly adopted to communicate that an API should be avoided, such as the project documentation, JSDoc annotation, code comment, console message, and deprecation utility. Indeed, there have been many studies on deprecation strategies and evolution mostly on Java, C#, and Python. However, to the best of our knowledge, there are no detailed studies aiming at analyzing how API deprecation changes over time in the JavaScript ecosystem. This paper provides an empirical study on how API deprecation evolves in JavaScript by analyzing 1,918 releases of 50 popular packages. Results show that close to 60% have rising trends in the number of deprecated APIs, while only 9.4% indicate a downward trend. Also, most deprecation occurrences are both added and removed on minor releases instead of removed on major releases, as recommended by best practices.