Newly revised Section 10 for ES3.1.

Mark S. Miller erights at
Wed Jul 9 19:12:37 PDT 2008

On Wed, Jul 9, 2008 at 7:02 PM, Brendan Eich <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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