This is great to have around, I hope you'll publish it! :)

I've published this notebook now, with your suggestions and some more details.

How do you feel about doing both measurements in the same loop? The result feels more representative to me, as you can see date being constantly in front of and behind performance.now.

One of the things that interesting to me (at least in default Firefox) how fast the iteration loops are on these, which would be erased if I combined them. That being said, no reason we can't have both. Thanks for the suggestion!