Hmm. If every library author took the second approach there would be tons of wasted code. This may not be a bad thing but it bothers my OCD. It would be nice

Hmm. If every library author took the second approach there would be tons of wasted code. This may not be a bad thing but it bothers my OCD. It would be nice if you could write callback-only or promise-only code and have a post-processor produce two .JS files. One with callbacks and one with promises. Then somehow, just as magically, you could require either one. This would save memory and my OCD.