ES 3.1 implementations?

[Douglas Crockford]

Robert Sayre wrote:
> I am putting together feedback on the JSON features proposed for ES
> 3.1, and I was wondering if there any ES 3.1 implementations
> available.
> 
> Given the limited scope of the spec, I would expect to see at least
> one implementation completed soon if there isn't one. Maybe in Rhino
> or something?

There is an implementation in JavaScript at http://json.org/json2.js.