Huh good to know:

  $ node
  > JSON.parse('1231231231231231231231231123123123123')
  1.2312312312312312e+36

I've heard of JSON implementations in other languages making bigger JSON numbers than javascript supports; but I didn't realise JSON.parse would quietly parse them and throw away precision in the process. I wonder what the plan is for JSON serialization support of bigints. I assume there is no plan - Chrome stable 67 supports bigints, but JSON.serialize(2n) throws a TypeError.