The JavaScript programming language is widely used in Web programming and is increasingly used for general purpose computing. Therefore, improving the correctness, security, and performance of JavaScript applications has been the driving force behind the study of language type systems, static analysis, and compiler technology. Many of these techniques are designed to control some of the most dynamic features of a language, but little seems to be known about how a programmer actually uses the language or these features. In this article, we make an empirical study of the dynamic behavior of the widely used JavaScript program corpus, and analyze how and why the dynamic characteristics are used.
