JSON is slightly worse than you describe - the JSON language doesn’t restrict you to 64bit floats, but most implementations do as you describe. On the other hand, the JSON language doesn’t support NaNs or infinities, so the union of language and implementation means that in practice JSON is strictly weaker than IEEE 754.
If you count by threes, the ones place is unique until you pass each multiple of 30 - 3, 6, 9, _8, _1, _4, where was I? I hadn’t made it to 30, ends with a 4, must be 24. 27, 30, 33, _6…
Serves as a sort of checksum, as long as you know roughly how many you have and just the last digit.
I find them vital for side projects - especially if they get set aside for a week/month/year, I sometimes will lose track of assumptions I’ve made or use cases for apis that tests tend to expose.
Sure you can encode all of that as comments, but unless you reread each file when you return from a break, you can’t always trace those thoughts and see where they lead. On the other hand if you “find all references” in your ide or change some implementation so that a test breaks, past-you can save the day with that extra information about what they intended at the time.
Another anecdote for your collection: my father fell off a ladder last year - not far enough to sustain any injury, but far enough to catch his ring slightly in trying to regain his balance. Finger ended up swelling enough that the ring was a problem, ended up having to be cut off.
I wouldn’t have imagined that a fall off of the second step of a ladder could result in the destruction of a 40 year old wedding ring either, but here we are!
We are mostly targeting enabling GWT applications to be able to (relatively seamlessly) update to J2CL as a compiler, but are definitely interested in apps or libraries starting their lives as a plain Java project and expose it to JS/TS/closure in a variety of ways.
Aside from the github repo, most of the conversation as we work on this happens at https://gitter.im/vertispan/j2cl - feel free to stop by to ask any questions or share a use case that seems under-represented.