Modern regular expressions (called regexes) depart significantly from traditional regular expressions, due to the addition of new features such as capture groups, lookarounds and backreferences. Different regex languages have different features with potentially different matching complexities, and complexity results for real-world regex languages are scarce. Our work focuses on JavaScript regexes, and provides an answer to the question of their matching complexity. We prove that JavaScript regex matching with expanded counted repetitions is PSPACE-complete, even without negative lookarounds. We are also in the process of proving that JavaScript regex matching without lookarounds (but still with expanded counted repetitions) is OptP-complete. Our results rely on core proofs mechanized in the Rocq proof assistant.