A tool used by anyone and everyone in the audio space: https://www.izotope.com/en/products/rx.html - it's most important feature is that while you can work on the waveform, that's pretty much the least useful way to work with audio, and so it also lets you work directly on the spectrogram of an audio source instead, which makes editing the actual sounds you hear much, much easier.

Reactive programming, possibly in js

Not in this context.

"RX 7, The industry standard for audio repair": https://www.izotope.com/en/products/rx.html

No, not even remotely. Izotope RX: https://www.izotope.com/en/products/rx.html