The most interesting part of this (the bypass itself) involves executing a Javascript challenge. It's very convenient to do that from Javascript (the author mentions that Python implementations need to add a Javascript interpreter). Besides that, it's mostly async I/O which: 1) might be annoying in earlier versions of Javascript, but with Promises and async/await, it's very clear and readable (to me) in Javascript; 2) is the exact case (I/O-bound, not CPU-bound) where Node.js performs efficiently.