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 wrot
> 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 transitio
> 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 magicall
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
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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 res
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
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
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
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
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