JavaScript API Deprecation in the Wild: A First Assessment

Building an application using third-party libraries is a common practice in software development. As any other software system, code libraries and their APIs evolve over time. In order to help version migration and ensure backward compatibility, a recommended practice during development is to deprecate API. Although studies have been conducted to investigate deprecation in some programming languages, such as Java and C#, there are no detailed studies on API deprecation in the JavaScript ecosystem. This paper provides an initial assessment of API deprecation in JavaScript by analyzing 50 popular software projects. Initial results suggest that the use of deprecation mechanisms in JavaScript packages is low. However, we find five different ways that developers use to deprecate API in the studied projects. Among these solutions, deprecation utility (i.e., any sort of function specially written to aid deprecation) and code comments are the most common practices in JavaScript. Finally, we find that the rate of helpful message is high: 67% of the deprecations have replacement messages to support developers when migrating APIs.