A random collection of ES4 draft spec surprises and thoughts

Mark S. Miller erights at google.com
Mon May 26 17:57:29 PDT 2008

On Mon, May 26, 2008 at 12:01 PM, Brendan Eich <brendan at mozilla.org> wrote:
> If I recall correctly (and I'm sure someone will set me straight otherwise),
> JSON is not compatible with ES3 -- Unicode non-BMP character handling
> differs. Trying to force a subset relation from JSON to ES4 is not going to
> fly if JSON is not a subset of ES3.

That's the first I've heard of that problem. AFAIK, JSON, ES3, ES3.1,
and ES4 all accept \u surrogate pairs representing a UTF-16 encoding
of non-BMP characters. Can anyone say more about what the remaining
problem is here?

The only breakage in the subset relationship that I'm aware of are

* the ES3 stripping of Cf characters, which everyone agrees needs to
be fixed in ES3.1 and ES4,

* and the treatment of \u2028 and \u2029 are newline characters rather
than merely whitespace characters. We're fixing this in ES3.1 and
proposing that ES4 fix this as well.

Are there other problems?


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