Newly revised Section 10 for ES3.1.

Allen Wirfs-Brock Allen.Wirfs-Brock at
Wed Jul 9 22:05:18 PDT 2008

I'm also confused about this.  My understanding was, other than perhaps some of the details I was specifically looking for feedback on, that what I specified was generally what ES4 was planning on doing.

From: es4-discuss-bounces at [mailto:es4-discuss-bounces at] On Behalf Of Mark S. Miller
Sent: Wednesday, July 09, 2008 7:13 PM
To: Brendan Eich
Cc: Herman Venter; Douglas Crockford; es3.x-discuss at; es4-discuss at; Pratap Lakshman (VJ#SDK)
Subject: Re: Newly revised Section 10 for ES3.1.

On Wed, Jul 9, 2008 at 7:02 PM, Brendan Eich <brendan at<mailto:brendan at>> wrote:
On Jul 9, 2008, at 6:58 PM, Mark S. Miller wrote:
Hi Maciej, IIUC, these examples work the same in Allen's proposal as the do in ES4. If this does break the web, doesn't ES4 have exactly the same problem?

The idea for ES4 was to change the meaning of function sub-statements only under opt-in versioning. Implementations would do whatever they do today without an explicit type="application/ecmascript;version=4" or equivalent "application/javascript;version=2" on the script tag.

I had not understood that. I knew that new keywords were switched by the ES4 opt-in, and I have been following what ES4 switches based on strictness, but I probably haven't paid enough attention to ES4 opt-in. Besides keywords, what other elements of ES4 are switched on opt-in rather than strictness? Are all four combinations of opt-in vs strictness possible? Is opt-in per execution context (script) or per global object (frame)? A link to the relevant docs is an adequate answer. Thanks.

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