Could also do like C# does and treat just `throw;` as an explicit rethrow...
I'm also not sure a lot of optimizations are needed as this is exception handling as otherwise mentioned. -- Michael J. Ryan - [email protected] - http://tracker1.info Please excuse grammar errors and typos, as this message was sent from my phone. On Mar 18, 2017 12:21 PM, "T.J. Crowder" <[email protected]> wrote: > I don't see optimization being a big deal, this is exception processing > after all. > > I was also thinking any expression: > > ```js > try { > // ... > } > catch (e if arbitraryExpression1Here) { > // ...handle case 1 > } > catch (e if arbitraryExpression2Here) { > // ...handle case 2 > } > ``` > > ...which would essentially be: > > ```js > try { > // ... > } > catch (e) { > if (arbitraryExpression1Here) { > // ...handle case 1 > } else if (arbitraryExpression2Here) { > // ...handle case 2 > } else { > throw e; > } > } > ``` > > ...but without messing up the reported source of the error/stack (I'm > looking at you, IE11). > > -- T.J. Crowder > > > On Sat, Mar 18, 2017 at 6:06 PM, Jordan Harband <[email protected]> wrote: > >> If the condition can be just "any javascript", wouldn't that potentially >> impede optimizations? Hopefully implementors can weigh in here, since >> non-implementor performance intuition (like mine) is often off base. >> >> On Sat, Mar 18, 2017 at 9:16 AM, kdex <[email protected]> wrote: >> >>> I'm not sure if embedding this idea into the language will make future >>> ideas about true pattern matching harder to implement or not. >>> Destructuring assignments are pretty slow from what I've measured, and >>> they still made it in, so I hardly see performance being a showstopper here. >>> >>> On Saturday, March 18, 2017 12:18:22 PM CET Michael J. Ryan wrote: >>> > The if condition doesn't need to be limited to instance of... >>> > >>> > catch (err if !isNaN(err.status)) >>> > >>> > Aside: entering code in a phone is hard... >>> > >>> > > `instanceof` doesn't work across realms (iframes, for example). If we >>> > > introduced conditional catch blocks, I'd want a more reliable >>> matching >>> > > mechanism than instanceof. >>> > > >>> > > On Fri, Mar 17, 2017 at 5:01 PM, Zach Lym <[email protected]> >>> wrote: >>> > > >>> > >> Firefox supports the following conditional `catch` syntax: >>> > >> >>> > >> try { >>> > >> let result = await (); >>> > >> } catch (e if e instanceof ErrorType) { >>> > >> ... >>> > >> } >>> > >> >>> > >> >>> > >> This was originally implemented in Spidermonkey as part of an ES >>> proposal >>> > >> around 2000, but it was rejected for unknown reasons [0]. A 2012 >>> email to >>> > >> this list suggesting standardization of the syntax was passed over >>> in favor >>> > >> of waiting for a generic pattern matching facility [0][1]. Later >>> > >> discussion suggests that the pattern matching proposal would have >>> been very >>> > >> slow [2]. A proposal for a Java-like type-based conditional was >>> proposed in >>> > >> 2016, but was criticized for lacking generality [2]. >>> > >> >>> > >> If the above summary is accurate, I would like to try to >>> standardize the >>> > >> vanilla syntax once again. It's imperative, general, and doesn't >>> preclude >>> > >> the use of any hypothetical pattern matching functionality. >>> > >> >>> > >> Javascript's control flow has improved dramatically in recent years: >>> > >> promises got rid of callbacks, `async`/`await` clipped promise >>> chains, and >>> > >> classes make it easy to create custom Error objects that preserve >>> > >> stacktraces. Conditional catch is the last bit of syntax needed to >>> make JS >>> > >> look like it was designed to handle asynchronous functions. >>> > >> >>> > >> Thoughts? >>> > >> >>> > >> -Zach Lym >>> > >> >>> > >> [0]: https://esdiscuss.org/topic/conditional-catch-clause#content >>> -10 >>> > >> [1]: https://esdiscuss.org/topic/conditional-catch >>> > >> [2]: https://esdiscuss.org/topic/error-type-specific-try-catch-bl >>> > >> ocks#content-14 >>> > >> >>> > >> _______________________________________________ >>> > >> es-discuss mailing list >>> > >> [email protected] >>> > >> https://mail.mozilla.org/listinfo/es-discuss >>> > >> >>> > >> >>> > > >>> > > _______________________________________________ >>> > > es-discuss mailing list >>> > > [email protected] >>> > > https://mail.mozilla.org/listinfo/es-discuss >>> > > >>> > > >>> > >>> >>> _______________________________________________ >>> es-discuss mailing list >>> [email protected] >>> https://mail.mozilla.org/listinfo/es-discuss >>> >>> >> >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss >> >> > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
_______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
