Unfortunately, in this period of time I am quite busy porting Paulstretch to Android. I have rewritten a (C++) fixed point implementation of Paulstretch and now I have to write the GUI for Android. After I will release it, I hope that I will have some time to port it to JS. Anyway, feel free to add the task for me (my user is 'paulnasca').

If you want to look at the algorithm of Paulstretch you can have a look to a simple Python implementation: https://github.com/paulnasca/paulstretch_python/blob/master/... The algorithm is pretty fast, the most time consuming operations are the FFTs and IFFTs. That's why I think that it might work on real-time JS.