Hello!

Thank you for this proposal and your hard work!

While waiting for the proposal to be generally available, I've implemented a custom JSON parser that is future-compatible with the proposal. It doesn't look feasible to make it a proper polyfill, considering that JS implementation will probably be slower and we can't detect new features usage, but it's a ponyfill that can be used today where needed.

I'm not sure that I've implemented all the features correctly, it's not that easy to follow the standard, but all the serialization examples should work correctly. I will be very grateful if someone could review the implementation.

Thanks!