I don't know more than anyone else about this particular situation, but I can imagine how JS reflection works. Something like:

    let test = function() { return "hello";}
    test.toString()

returns

    "function() { return "hello";}" 

It's not too difficult to imagine that pairing that with some JS parsing would allow you to slowly crawl your way around an app and gather the app structure. Crazy, and fascinating idea.