Es4-discuss Digest, Vol 8, Issue 44

Brendan Eich brendan at
Tue Oct 30 16:58:12 PDT 2007

On Oct 30, 2007, at 3:59 PM, Yehuda Katz wrote:

> I would specifically like to hear a realistic technical scenario  
> where the implementation of ES4 produces serious complications in  
> the open web.

Me too. Here's one analysis of how ES4 might break existing scripts:

* New keywords and syntax hanging off them. Already addressed by not  
opening the __ES4__ namespace without opt-in version selection, e.g.  
by <script type="application/ecmascript;version=4">. See the  
versioning proposal at

* Intentional incompatibilities. Today we knocked down three proposed  
such changes:

* Unintended incompatibilities: these have to be addressed by testing  
the reference implementation, other implementations, and the spec- 
language (run by one's brain). This is an auditing procedure, QA.  
Often coverage is a problem, but we have had good experiences with  
fuzz-testing JS and intend to fuzz the RI.

Hope this helps.


More information about the Es4-discuss mailing list