Versioning?

Mark S. Miller erights at google.com
Mon Dec 19 10:48:12 PST 2011


On Mon, Dec 19, 2011 at 10:21 AM, Xavier MONTILLET
<xavierm02.net at gmail.com>wrote:

> Why
>
> use version 6;
>
> and not
>
> "use version 6";
>
> ? Just to be sure ES 6 code breaks in old browsers ?
> And what do you mean by "opt-in for ES6" ? New syntax ? Everything in ES 6
> ?
>
> I'm thinking about weakmaps:
> - on the one hand, you want to use native weakmaps when available so
> you would want to "opt-in for ES6"
> - but on the other hand, you could also implement a weakmap "polyfill"
> that wouldnt be as efficient, that would suck the memory but still
> work, and have it work in older browsers
>

http://code.google.com/p/google-caja/source/browse/trunk/src/com/google/caja/ses/WeakMap.js
is a WeakMap polyfill that should work *transparently* in all ES5
conformant browsers. It is indeed not as efficient, but it's better than
you might expect ;).

Btw, where does the term "polyfill" come from?




>
> Therefore, setting the thing to do to "opt-in for ES6" to something
> not backward compatible doesn't seem like a good idea to me.
>
> On Mon, Dec 19, 2011 at 1:42 PM, David Bruant <bruant.d at gmail.com> wrote:
> > I did start a related thread a while ago [1].
> >
> > Brendan's response [2] explained a few things:
> > "Please read RFC 4329:
> >
> > http://tools.ietf.org/html/rfc4329
> >
> > There will be *at least* a ;version=6 parameter you can use, probably
> > with either application/javascript and application/ecmascript -- I have
> > argued that we should align version numbers."
> >
> >
> > "Beyond the RFC 4329 version= parameter, we also want a pragma for
> > in-script-content version assertion:
> >
> >  use version 6;"
> >
> > See the full response [2] for full context.
> >
> > Besides an es-discuss thread, I think that what is really needed is an
> > harmony proposal. How to opt-in for ES6 is outside of the scope of pure
> > ECMAScript (especially if it's with playing with the HTML script tag
> > @type attribute), but let's face it, web devs need this information and
> > a wiki page on the topic would be handy.
> >
> > At the time of reading Brendan's response, I didn't have anything to add
> > on that and I still don't. Unlike HTML and CSS, JavaScript needs new
> > syntax features. Syntax features that are NOT backward compatible with
> > ES3. If you use one of these features, your script break in older
> > browsers (unlike new HTML elements and CSS rules).
> > I don't see an alternative to versionning. Smarter people are welcome to
> > jump in, I guess.
> >
> > David
> >
> > [1]
> https://mail.mozilla.org/pipermail/es-discuss/2011-August/016262.html
> > [2]
> https://mail.mozilla.org/pipermail/es-discuss/2011-August/016267.html
> >
> > Le 19/12/2011 11:49, Peter van der Zee a écrit :
> >> https://lists.webkit.org/pipermail/webkit-dev/2011-December/018924.html
> >>
> >> ``use version 6;``
> >>
> >> In which thread on esdiscuss should I have read about that?
> >>
> >> - peter
> >> _______________________________________________
> >> es-discuss mailing list
> >> es-discuss at mozilla.org
> >> https://mail.mozilla.org/listinfo/es-discuss
> >
> > _______________________________________________
> > es-discuss mailing list
> > es-discuss at mozilla.org
> > https://mail.mozilla.org/listinfo/es-discuss
> _______________________________________________
> es-discuss mailing list
> es-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>



-- 
    Cheers,
    --MarkM
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20111219/1e908f6b/attachment-0001.html>


More information about the es-discuss mailing list