Re: [webkit-dev] Preferred style for checking for undefined in our built-in JavaScript code?
I've just prototyped bytecode intrinsic constants; enhancing bytecode intrinsic mechanism to accept the form `@xxx`. (not `@xxx(...)`, it is already introduced). And implement @undefined with this. https://bugs.webkit.org/show_bug.cgi?id=153737 On Tue, Dec 1, 2015 at 7:00 AM, Geoffrey Garen wrote: > > Seems like we should not have to wait long for the “long term”. It seems > that the built-in compiler could start magically transforming “@undefined” > instead of magically transforming “undefined” any time we like; likely a > simple find and replace job. Or it could do both during a transition > period. It could even treat a bare “undefined” as an error if we are > worried that we will make that error. > > Yup. > > Geoff > ___ > webkit-dev mailing list > webkit-dev@lists.webkit.org > https://lists.webkit.org/mailman/listinfo/webkit-dev > ___ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
Re: [webkit-dev] Preferred style for checking for undefined in our built-in JavaScript code?
> Seems like we should not have to wait long for the “long term”. It seems that > the built-in compiler could start magically transforming “@undefined” instead > of magically transforming “undefined” any time we like; likely a simple find > and replace job. Or it could do both during a transition period. It could > even treat a bare “undefined” as an error if we are worried that we will make > that error. Yup. Geoff ___ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
Re: [webkit-dev] Preferred style for checking for undefined in our built-in JavaScript code?
> On Nov 30, 2015, at 11:57 AM, Geoffrey Garen wrote: > > For the time being, I like “x === undefined”. > > Long term, I’d like us to switch to “x === @undefined”. > > We use @ to indicate reserved words in built-ins. Currently, “@undefined" > does not exist, but the built-in compiler magically transforms “undefined” a > safe reserved word. > > The typeof and void 0 code should be fast, but I find it obtuse. Thanks for all the answers, everyone. I like Geoff’s proposal. Seems like we should not have to wait long for the “long term”. It seems that the built-in compiler could start magically transforming “@undefined” instead of magically transforming “undefined” any time we like; likely a simple find and replace job. Or it could do both during a transition period. It could even treat a bare “undefined” as an error if we are worried that we will make that error. Then perhaps later we could relieve the built-in compiler of those responsibilities if we think that’s important. — Darin ___ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
Re: [webkit-dev] Preferred style for checking for undefined in our built-in JavaScript code?
On Mon, Nov 30, 2015 at 11:37 AM, Darin Adler wrote: > I see the following in some code: > > if (xxx === undefined) FWIW, I always use this style. - R. Niwa ___ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
Re: [webkit-dev] Preferred style for checking for undefined in our built-in JavaScript code?
Web Inspector’s frontend code tends to use “x === undefined”, as we’ve found it the easiest to read. > On Nov 30, 2015, at 11:57 AM, Geoffrey Garen wrote: > > For the time being, I like “x === undefined”. > > Long term, I’d like us to switch to “x === @undefined”. > > We use @ to indicate reserved words in built-ins. Currently, “@undefined" > does not exist, but the built-in compiler magically transforms “undefined” a > safe reserved word. > > The typeof and void 0 code should be fast, but I find it obtuse. > > Geoff > >> On Nov 30, 2015, at 11:39 AM, Filip Pizlo wrote: >> >> I’ve also been guilty of: >> >> if (xxx === void 0) >> >> This is slightly better than saying “undefined”, since that’s not actually a >> reserved word. >> >> I believe that all of these should perform the same. We should pick one >> based on what looks nicest and what has the most clear semantics. >> >> -Filip >> >> >> >>> On Nov 30, 2015, at 11:37 AM, Darin Adler wrote: >>> >>> I see the following in some code: >>> >>> if (xxx === undefined) >>> >>> And I see the following in some other code: >>> >>> if (typeof xxx == “undefined”) >>> >>> or >>> >>> if (typeof xxx === “undefined”) >>> >>> Is one preferred over the other, style-wise? Is one more efficient than the >>> other? >>> >>> — Darin >>> ___ >>> webkit-dev mailing list >>> webkit-dev@lists.webkit.org >>> https://lists.webkit.org/mailman/listinfo/webkit-dev >> >> ___ >> webkit-dev mailing list >> webkit-dev@lists.webkit.org >> https://lists.webkit.org/mailman/listinfo/webkit-dev > > ___ > webkit-dev mailing list > webkit-dev@lists.webkit.org > https://lists.webkit.org/mailman/listinfo/webkit-dev ___ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
Re: [webkit-dev] Preferred style for checking for undefined in our built-in JavaScript code?
FWIW, performance seems to be equivalent: http://jsperf.com/typeof-vs-undefined-check/39 Chris https://chrismatic.io/ > On Nov 30, 2015, at 1:01 PM, Geoffrey Garen wrote: > > For the time being, I like “x === undefined”. > > Long term, I’d like us to switch to “x === @undefined”. > > We use @ to indicate reserved words in built-ins. Currently, “@undefined" > does not exist, but the built-in compiler magically transforms “undefined” a > safe reserved word. > > The typeof and void 0 code should be fast, but I find it obtuse. > > Geoff > >> On Nov 30, 2015, at 11:39 AM, Filip Pizlo wrote: >> >> I’ve also been guilty of: >> >>if (xxx === void 0) >> >> This is slightly better than saying “undefined”, since that’s not actually a >> reserved word. >> >> I believe that all of these should perform the same. We should pick one >> based on what looks nicest and what has the most clear semantics. >> >> -Filip >> >> >> >>> On Nov 30, 2015, at 11:37 AM, Darin Adler wrote: >>> >>> I see the following in some code: >>> >>> if (xxx === undefined) >>> >>> And I see the following in some other code: >>> >>> if (typeof xxx == “undefined”) >>> >>> or >>> >>> if (typeof xxx === “undefined”) >>> >>> Is one preferred over the other, style-wise? Is one more efficient than the >>> other? >>> >>> — Darin >>> ___ >>> webkit-dev mailing list >>> webkit-dev@lists.webkit.org >>> https://lists.webkit.org/mailman/listinfo/webkit-dev >> >> ___ >> webkit-dev mailing list >> webkit-dev@lists.webkit.org >> https://lists.webkit.org/mailman/listinfo/webkit-dev > > ___ > webkit-dev mailing list > webkit-dev@lists.webkit.org > https://lists.webkit.org/mailman/listinfo/webkit-dev ___ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
Re: [webkit-dev] Preferred style for checking for undefined in our built-in JavaScript code?
For the time being, I like “x === undefined”. Long term, I’d like us to switch to “x === @undefined”. We use @ to indicate reserved words in built-ins. Currently, “@undefined" does not exist, but the built-in compiler magically transforms “undefined” a safe reserved word. The typeof and void 0 code should be fast, but I find it obtuse. Geoff > On Nov 30, 2015, at 11:39 AM, Filip Pizlo wrote: > > I’ve also been guilty of: > > if (xxx === void 0) > > This is slightly better than saying “undefined”, since that’s not actually a > reserved word. > > I believe that all of these should perform the same. We should pick one > based on what looks nicest and what has the most clear semantics. > > -Filip > > > >> On Nov 30, 2015, at 11:37 AM, Darin Adler wrote: >> >> I see the following in some code: >> >> if (xxx === undefined) >> >> And I see the following in some other code: >> >> if (typeof xxx == “undefined”) >> >> or >> >> if (typeof xxx === “undefined”) >> >> Is one preferred over the other, style-wise? Is one more efficient than the >> other? >> >> — Darin >> ___ >> webkit-dev mailing list >> webkit-dev@lists.webkit.org >> https://lists.webkit.org/mailman/listinfo/webkit-dev > > ___ > webkit-dev mailing list > webkit-dev@lists.webkit.org > https://lists.webkit.org/mailman/listinfo/webkit-dev ___ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
Re: [webkit-dev] Preferred style for checking for undefined in our built-in JavaScript code?
I’ve also been guilty of: if (xxx === void 0) This is slightly better than saying “undefined”, since that’s not actually a reserved word. I believe that all of these should perform the same. We should pick one based on what looks nicest and what has the most clear semantics. -Filip > On Nov 30, 2015, at 11:37 AM, Darin Adler wrote: > > I see the following in some code: > >if (xxx === undefined) > > And I see the following in some other code: > >if (typeof xxx == “undefined”) > >or > >if (typeof xxx === “undefined”) > > Is one preferred over the other, style-wise? Is one more efficient than the > other? > > — Darin > ___ > webkit-dev mailing list > webkit-dev@lists.webkit.org > https://lists.webkit.org/mailman/listinfo/webkit-dev ___ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
