Re: How to manipulate integer that sometimes Nan and sometimes have a value?

Path	csiph.com!news.swapon.de!weretis.net!feeder1.news.weretis.net!news.solani.org!.POSTED!not-for-mail
From	Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups	comp.lang.javascript
Subject	Re: How to manipulate integer that sometimes Nan and sometimes have a value?
Date	Sun, 27 Sep 2015 13:50:13 +0200
Organization	PointedEars Software (PES)
Lines	51
Message-ID	<5607D7F5.2000607@PointedEars.de> (permalink)
References	<9060ce04-2f9e-4554-be83-2f69c213424f@googlegroups.com> <4f31ec16-109f-43b2-9d50-b39d4fb47f84@googlegroups.com> <3cf46737-de54-489e-9d9d-89413b18c099@googlegroups.com> <87wpvdec2d.fsf@bsb.me.uk> <64092fce-7ef7-48d7-9e0d-27a2220fcfe0@googlegroups.com> <XnsA5219A84E49A9eejj99@194.109.6.166> <4175397.OLgykfH8RQ@PointedEars.de> <XnsA521E8950918Ceejj99@194.109.6.166>
Reply-To	Thomas 'PointedEars' Lahn <cljs@PointedEars.de>
Mime-Version	1.0
Content-Type	text/plain; charset=windows-1252
Content-Transfer-Encoding	8bit
X-Trace	solani.org 1443354613 10729 eJwFwQEBwDAIAzBNDNoOOXCGfwlP4DR+CoKBxcbIwX5pliYNcdRR+dZxbupuz6WW9aQ6+QMJlBCg (27 Sep 2015 11:50:13 GMT)
X-Complaints-To	abuse@news.solani.org
NNTP-Posting-Date	Sun, 27 Sep 2015 11:50:13 +0000 (UTC)
User-Agent	Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.7.0
X-User-ID	eJwFwYEBwDAEBMCVKP8YhyT2H6F3MCpPOEHHYtkW+XW5H202uTdavyJQ8BTUDckWa33PbAYxczuz7kJqfjRlFQ8=
In-Reply-To	<XnsA521E8950918Ceejj99@194.109.6.166>
Cancel-Lock	sha1:L8WDxddC4RxQnd4fDNFc/2Xqsu0=
X-NNTP-Posting-Host	eJwFwYEBwCAIA7CXhEKVcwba/09YkqBxdjAZqRSEtjrjnomSX+M6pHqWN0I7vpGLePC6jz8NPxDX
Xref	csiph.com comp.lang.javascript:28743

Show key headers only | View raw

Evertjan. wrote:

> Thomas 'PointedEars' Lahn […] wrote […]:
>> Evertjan. wrote:
>>> What you probably mean is that the element may be
>>> EITHER undefined
>>> OR hold null OR a string OR an object.
>>>
>>> When testing with
>>>
>>> isNaN(element)
>>>
>>> it will return "true" because isNaN() returns true in all these cases.
>>
>>   isNaN("42") === false
>>   isNaN({valueOf: function () { return 42; }}) === false
>>   isNaN({toString: function () { return "42"; }}) === false
>
> Indeed,
> "42" being a string,
> the other two are objects.

Exactly.  (_Object references_, to be precise.)

> There must be a point of no return somewhere,
> because otherwise what would be the point of it all?

I have no idea what you mean.

You did not realize, and my examples show, that isNaN(value) returns “false”
if ToNumber(value) is not NaN.  For object references, this is the primitive
representation of the object referred to by “value”, with a preference on
value.valueOf(), and value.toString() as fallback.  For string values (which
can also be returned by .toString()) it suffices if “value” can be
interpreted as an expansion of /StringNumericLiteral/.  Therefore, in
general your statement is wrong.

Another example:

  isNaN(["42"]) === isNaN([42]) === false

<http://www.ecma-international.org/ecma-262/6.0/index.html#sec-isnan-number>

Number.isNaN() was introduced in ECMAScript 2015 because isNaN() does this
conversion and interpretation.

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | SVN: <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | ES Matrix: <http://PointedEars.de/es-matrix>
Please do not cc me. / Bitte keine Kopien per E-Mail.

Thread

csiph-web