Presenter: Vitalis Salis
Date: 22 November 2017

JavaScript is one of the most important elements of the web. It is being used by the majority of websites and it is supported by all modern browsers. We present the rst large-scale study of client- side JavaScript code evolution. Speci cally, we have been collecting and storing JavaScript code from Alexa’s top 10000 websites on a daily basis (∼7.5 gb per day), for nine consecutive months. We have analyzed the resulting dataset to study how often developers deploy new scripts on the server-side. Our results indicate that the lifespan of scripts is quite short. That is, ve days for external scripts and one day for internal JavaScript code. In addition, we have examined how common JavaScript code reuse and especially the reliance to third-party libraries. Furthermore, we observed how software bugs evolve over time. To do so, we employed well-known static analysis tools to identify potential software bugs on the various scripts and then observed if they increase or decrease over time.