On Jan 5, 2012, at 8:30 AM, Axel Rauschmayer wrote:
> On Jan 5, 2012, at 1:56 , Brendan Eich wrote:
>
>> Better to dispense with modes or ordered versions altogether, which is the
>> key idea of the proposal.
>
>
> So, simplified, the story is:
>
> - ES6 is a superset of ES5.strict.
That's always been promised.
> - ES{3,5}.non-strict is neither a subset nor a superset of ES6, it has to be
> handled differently.
>
> If these modes (strict versus non-strict) exist, then I would want a per-file
> marker for strict code:
> - "use strict";
This doesn't mean Harmony, though. Not now, in ES5 implementations -- it means
only ES5-strict. And not in dowrev impls, where it means nothing (and semantics
differ at runtime).
> - use strict;
This is a good idea but it was not proposed by Dave to mean Harmony opt-in.
Rather, |use module;| was, as a way to avoid bracing and indenting a top level
hunk of code in an anonymous module {...} declaration.
> - module {
>
>
> Compared to languages such as Java, JavaScript additionally faces the
> challenge that a developer can’t control what language version is implemented
> by the browser. How will that be handled? Sketching a solution would provide
> a more complete picture of how to migrate to ES6.
APIs can be object-detected. New syntax requires autoconf-style eval/Function
tests. All doable, nothing mysterious, some try/catch pain required.
I rather expect a boot-loader script will use more coarse-grained means of
deciding what to fetch. We had proposed a way to reflect on the maximum
supported version (__ECMASCRIPT_VERSION__, IIRC) but that was unsatisfying.
More to do here.
/be
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