Allow negative durations?

[thojanssens]

I'm having the following error when specifying a negative duration:

ecmascript.mjs:363 Uncaught (in promise) RangeError: negative values not allowed as duration fields

Does that mean that I have to bloat my code with if's to call the appropriate function plus/minus according to the sign of the given duration?

[ptomato]

Yes, negative durations seems to be the area that we are getting the strongest feedback about. The current discussion is on #558, so I'd like to consolidate this into that one.