An Exploratory Study of Analyzing JavaScript Online Code Clones

Online code clones occur due to reusing code snippets in software repositories from online resources such as GitHub and Stack Overflow. Previous works have shown that snippets from Stack Overflow are reused in other open-source projects and vice versa. Analysis of online code reusing patterns could identify outdated code, understand developers' practices, and help to design new code search engines. This study analyzed JavaScript online code clones between Stack Overflow and GitHub repositories. We first developed a JavaScript code corpus to search online clones. The clone search results reported 12,579 online clones between 276,547 non-trivial syntactically validated Stack Overflow snippets and 292 GitHub repositories. We manually classified the top 10% (1257) pairs of clones in seven online clone patterns. We observed that around 70% of JavaScript snippets in Stack Overflow posts are copied from GitHub repositories or from other external sources. Moreover, only 30.59% of JavaScript Snippets in Stack Overflow accepted answers could be considered as reusable snippets.