ABSTRACT Context Reactive Programming (RP) provides powerful abstractions for managing asynchronous and event‐driven behaviors, but its APIs are often perceived as complex and difficult to use, particularly due to their reliance on functional programming concepts. Objective This study investigates the usability of two prominent JavaScript RP libraries, RxJS and Bacon.js, to identify common usability issues and suggest improvements. Method A mixed‐method evaluation was conducted. First, objective structural metrics were applied to assess the libraries' design. Then, a user‐centered study was performed involving programming tasks, a post‐task questionnaire based on the Cognitive Dimensions of Notation (CDN) framework, and follow‐up interviews. Results Both libraries exhibited moderate usability. Metrics revealed strengths in reusability and parameter design, while user studies highlighted challenges in learnability, error handling, and documentation. RxJS generally performed better in metrics, while Bacon.js had stronger task completion rates. Conclusion The findings suggest that despite their popularity, RP APIs can still hinder adoption due to usability issues. Improvements such as enhanced documentation, guided error‐handling strategies, and reduced operator complexity can significantly improve developer experience.

Conventionally, callbacks and inversion of control have been the main tools to structure event-driven applications. Sadly, those patterns constitute a well-known source of design problems. The Reactive Programming (RP) paradigm has arisen as an approach to mitigate these problems. Yet, little evidence has been provided regarding the advantages of RP, and concerns have also arisen about the API usability of RP libraries given their disparate number of operators. In this work, we conduct a study on GitHub (GH) and Stack Overflow (SO) and explore three Reactive Extensions (Rx) libraries (RxJava, RxJS, and RxSwift) with the most GH projects to understand how much the vast Rx operators are being used. Also, we examine Rx SO posts to complement the results from the GH exploration by understanding the problems faced by RP developers and how they relate with the operators' frequencies found in open source projects. Results reveal that, in spite of its API size, the great majority of the Rx operators are actually being used (95.2%), with only a few, mostly related to RxJava, not being utilized. Also, we unveil 23 topics from SO with more posts concerning the Stream Abstraction (36.4%). Posts related to Dependency Management, Introductory Questions, and iOS Development figure as relevant topics to the community. The findings herein present can not only stimulate advancements in the field by understanding the usage of RP API and the main problems faced by developers, but also help newcomers in identifying the most important operators and the areas that are the most likely to be relevant for a RP application.

In 2020, due to the COVID-19 pandemic, educational activities had to be done remotely as a way to avoid the spread of the disease. Instead of shifting to an online learning model, it consisted of a transition to what was called Emergency Remote Teaching. This is a strategy to keep activities going on until it is safe again to return to the physical facilities of universities. This new setting became a challenge to both teachers and students. The lack of interaction and classroom socialization became obstacles for students to continue engaged.