I'm definitely open to changing the compiler. Not sure what the right
answer is. Since we are theoretically writing AS, I'd lean away from
using "void 0".
_responseHeaders is an Array, so in Flash, it cannot be undefined, only
null.
So, I think in code that is used in both SWF and JS, the developer will
write
if (_responseHeaders == null)
Wouldn't that work on both platforms?
I'd be tempted to just have the transpiler skip reporting any error if you
write:
if (_responseHeaders === undefined)
Thoughts?
-Alex
On 3/18/17, 10:09 PM, "Justin Mclean" <jus...@classsoftware.com> wrote:
>Hi,
>
>I was looking at HTTPService.as and noticed this:
>
>Given the variable _responseHeaders is declared is there any reason to do
>this:
>if (typeof _responseHeaders === 'undefined') {
>
>When this should work:
>if (_responseHeaders === undefined)
>
>I note this [1] says to avoid the style currently used in the code and
>other places (from a quick google search) suggest it's only needed for
>very old browsers (IE8) and where you are concerned that undefined may of
>been redefined.
>
>However changing this give an warning like so:
>Illogical comparison with undefined. Only untyped variables (or
>variables of type *) can be undefined.
>
>For code inside COMPILE_JS is this actually correct? Looks like a bug to
>me.
>
>This can be got around by using “void 0” like so:
>if (_responseHeaders === void 0)
>
>Seems to be a more modern way of doing the same thing and dosn’t raise a
>warning.
>
>Both methods are faster by about 10% than typeof X === 'undefined' in
>browsers I checked. [2]
>
>Thanks,
>Justin
>
>1.
>https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdeveloper
>.mozilla.org%2Fen%2Fdocs%2FWeb%2FJavaScript%2FReference%2FGlobal_Objects%2
>Fundefined&data=02%7C01%7C%7C5606c4b8afdc40c66ee608d46e863c18%7Cfa7b1b5a7b
>34438794aed2c178decee1%7C0%7C0%7C636254970223388353&sdata=GWAzyxYCvnUc9fx0
>DdU1HGOLIGwuSmOrZpYwTynYRoI%3D&reserved=0
><https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdevelope
>r.mozilla.org%2Fen%2Fdocs%2FWeb%2FJavaScript%2FReference%2FGlobal_Objects%
>2Fundefined&data=02%7C01%7C%7C5606c4b8afdc40c66ee608d46e863c18%7Cfa7b1b5a7
>b34438794aed2c178decee1%7C0%7C0%7C636254970223388353&sdata=GWAzyxYCvnUc9fx
>0DdU1HGOLIGwuSmOrZpYwTynYRoI%3D&reserved=0>
>2.
>https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fjsperf.co
>m%2Ftypeof-vs-undefined-check%2F37&data=02%7C01%7C%7C5606c4b8afdc40c66ee60
>8d46e863c18%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C63625497022338835
>3&sdata=DKX0LzIj41nCWNrbiVtYKB23vMJBlwMVhP8dCHHlivc%3D&reserved=0
><https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fjsperf.c
>om%2Ftypeof-vs-undefined-check%2F37&data=02%7C01%7C%7C5606c4b8afdc40c66ee6
>08d46e863c18%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C6362549702233883
>53&sdata=DKX0LzIj41nCWNrbiVtYKB23vMJBlwMVhP8dCHHlivc%3D&reserved=0>
>
