Analyzing Class Usage in Java']JavaScript Programs

JavaScript is originally a prototype-based, object-oriented language, but in 2015, ECMAScript 2015 (ES2015) introduced a syntax sugar that enables the class-based programming style. However, the use of the class syntax is not mandatory, and it is not clear to what extent classes are used in practice. It is also possible to use both the class-based style and the prototype-based style together, or to write a program like a procedural language without using either of them. In this study, we analyse 636 JavaScript projects developed since the introduction of the class syntax to determine the actual usage of classes. The result of our analysis shows that 51.3% of the projects use the class syntax, which is higher than the percentage of projects that use only the prototype syntax without the class syntax, indicating that JavaScript project development is shifting from prototype-based to class-based.