I've looked at some bytebeats with reverb and I've tried to understand how it works. From what I understand, it seems to me that it works something like this:
- Declare an Array object and fill it with 0s

- Take your "melody" or whatever and add <Array>.shift() to it

- Push that divided by a number??? (like 3) maybe??? into the array

- Set the output to the "melody"

I still don't have a good idea of this. I tried doing this myself:

t?0:d=Array(2000).fill(0),main=sin(t/4)/4+d.shift(),d.push(main),main

Dollchan
it's messy lol xD

Dividing main by 2 or larger in d.push(main) gives a different result: I hear a bit of bounciness and the tone comes back. I turned the ample rate down to 8000 and I heard it wasn't a smooth decrease; it seems to "step". Lastly, I decided to use a number between 1 and 2 and the fading is slower, but I could still tell I did it wrong because of the "stepping".