Rexstepper: a Reference Debugger for JavaScript Regular Expressions.

Regular expressions are notoriously difficult to get right, with developers often having to resort to trial-and-error approaches. Even so, little attention has been given by the research community to the development of effective debugging tools for regular expressions. We present RexStepper, a reference debugger for troubleshooting JavaScript regular expressions in the browser. RexStepper is implemented on top of RexRef, a trusted reference implementation of JavaScript (ECMAScript 5) regular expressions, which works by transpiling the given regular expression to a JavaScript function that recognises its expansions. We demonstrate the usefulness of RexStepper by successfully using it to troubleshoot a benchmark of 18 faulty regular expressions obtained from the Stack Overflow and Stack Exchange websites.