Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.lang.javascript > #18689
| Message-ID | <2081372.r8gXD5iYSO@PointedEars.de> (permalink) |
|---|---|
| From | Thomas 'PointedEars' Lahn <PointedEars@web.de> |
| Organization | PointedEars Software (PES) |
| Date | 2013-03-02 12:49 +0100 |
| Subject | Re: Why is this returning NaN |
| Newsgroups | comp.lang.javascript |
| References | (4 earlier) <kgqfsg$vdj$1@speranza.aioe.org> <1652233.QWaZaUHVxr@PointedEars.de> <kgr6co$5l3$1@speranza.aioe.org> <3738380.KODd8mRBzQ@PointedEars.de> <OOidnXA2nqcEHazMnZ2dnUVZ_r-dnZ2d@earthlink.com> |
Patricia Shanahan wrote: > On 3/1/2013 1:35 PM, Thomas 'PointedEars' Lahn wrote: >> […] I did not say that isNaN(…) was reliable with non-Number >> values; only that NaN, a Number value, can only be detected with >> isNaN(…). > > That is surprising. In environments that did not have an isNaN > equivalent, or when implementing the equivalent of isNaN for a library, > I used to use the property that a NaN is not equal to itself > but all other numbers are: > > if(!(x == x)) > > Does something go wrong with that? No, I do not think so. It appears to be equivalent to if (isNaN(x)) based on the premise that the value of x is of the Number type (an implementation of IEEE-754 floating-point values). This can be expressed as: if (typeof x == "number" && x != x) (Those who prefer “!==” here may do so with no obvious performance gain but with reduced backwards compatibility.) > Of course, isNaN is the clearest, most readable way of detecting a NaN, > regardless of whether it is the only way. With the provision that one must make sure first that the value is of the Number type, as the ECMAScript isNaN(…) is about whether the argument can be *interpreted* as a Number value. But I have yet to come across a case where I would use isNaN(…) and could not reasonably assume that the argument was a Number or something used as a Number later on. -- PointedEars Twitter: @PointedEars2 Please do not Cc: me. / Bitte keine Kopien per E-Mail.
Back to comp.lang.javascript | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Why is this returning NaN "Tony" <tony.johansson@inport.com> - 2013-02-26 11:54 +0100
Re: Why is this returning NaN Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-02-26 12:09 +0100
Re: Why is this returning NaN "Jukka K. Korpela" <jkorpela@cs.tut.fi> - 2013-02-26 13:45 +0200
Re: Why is this returning NaN "J.R." <groups_jr-1@yahoo.com.br> - 2013-03-01 00:45 -0300
Re: Why is this returning NaN "J.R." <groups_jr-1@yahoo.com.br> - 2013-03-01 01:13 -0300
Re: Why is this returning NaN Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-01 12:48 +0100
Re: Why is this returning NaN "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-03-01 10:06 +0100
Re: Why is this returning NaN Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-01 12:46 +0100
Re: Why is this returning NaN John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-01 14:19 +0000
Re: Why is this returning NaN "Joao Rodrigues (J.R.)" <groups_jr-1@yahoo.com.br> - 2013-03-01 12:01 -0300
Re: Why is this returning NaN Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-01 21:03 +0100
Re: Why is this returning NaN "Joao Rodrigues (J.R.)" <groups_jr-1@yahoo.com.br> - 2013-03-01 18:25 -0300
Re: Why is this returning NaN Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-01 22:35 +0100
Re: Why is this returning NaN Patricia Shanahan <pats@acm.org> - 2013-03-01 20:31 -0800
Re: Why is this returning NaN Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-02 12:49 +0100
Re: Why is this returning NaN "J.R." <groups_jr-1@yahoo.com.br> - 2013-03-03 12:32 -0300
Re: Why is this returning NaN "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-03-03 18:03 +0100
Re: Why is this returning NaN Martin Leese <please@see.Web.for.e-mail.INVALID> - 2013-03-03 10:16 -0700
OT: "javascript" was: Why is this returning NaN Christoph Becker <cmbecker69@gmx.de> - 2013-03-03 20:35 +0100
Re: OT: "javascript" was: Why is this returning NaN "Jukka K. Korpela" <jkorpela@cs.tut.fi> - 2013-03-03 21:43 +0200
Re: OT: "javascript" was: Why is this returning NaN Tim Streater <timstreater@greenbee.net> - 2013-03-03 19:45 +0000
"javascript" (was: OT: "javascript") Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-03 21:09 +0100
Re: "javascript" "J.R." <groups_jr-1@yahoo.com.br> - 2013-03-03 23:19 -0300
Re: "javascript" Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-04 11:27 +0100
Re: "javascript" Tim Streater <timstreater@greenbee.net> - 2013-03-04 13:09 +0000
Re: "javascript" Christoph Becker <cmbecker69@gmx.de> - 2013-03-10 20:50 +0100
Re: "javascript" Tim Streater <timstreater@greenbee.net> - 2013-03-10 20:29 +0000
Re: "javascript" Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-10 23:23 +0100
Re: "javascript" Tim Streater <timstreater@greenbee.net> - 2013-03-10 22:48 +0000
Re: "javascript" Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-10 23:53 +0100
Re: "javascript" Tim Streater <timstreater@greenbee.net> - 2013-03-10 23:23 +0000
Re: "javascript" Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-11 02:57 +0100
Re: "javascript" Tim Streater <timstreater@greenbee.net> - 2013-03-11 08:55 +0000
Re: "javascript" Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-11 17:38 +0100
Re: "javascript" Dr J R Stockton <reply1300@merlyn.demon.co.uk.invalid> - 2013-03-12 19:29 +0000
Re: "javascript" Andrew Poulos <ap_prog@hotmail.com> - 2013-03-13 14:36 +1100
Re: "javascript" John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-13 15:20 +0000
Re: "javascript" Andrew Poulos <ap_prog@hotmail.com> - 2013-03-14 11:18 +1100
Re: "javascript" John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-14 10:43 +0000
Re: "javascript" Andrew Poulos <ap_prog@hotmail.com> - 2013-03-15 07:02 +1100
Re: "javascript" John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-15 10:28 +0000
Re: "javascript" Andrew Poulos <ap_prog@hotmail.com> - 2013-03-16 07:17 +1100
Re: "javascript" John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-16 12:04 +0000
Re: "javascript" Andrew Poulos <ap_prog@hotmail.com> - 2013-03-17 08:17 +1100
Re: "javascript" John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-17 11:13 +0000
Re: "javascript" Andrew Poulos <ap_prog@hotmail.com> - 2013-03-17 23:15 +1100
Re: "javascript" John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-17 16:42 +0000
Re: "javascript" Andrew Poulos <ap_prog@hotmail.com> - 2013-03-18 07:47 +1100
Re: "javascript" John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-18 15:01 +0000
Re: "javascript" Andrew Poulos <ap_prog@hotmail.com> - 2013-03-19 07:34 +1100
Re: "javascript" John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-19 15:04 +0000
Re: "javascript" Andrew Poulos <ap_prog@hotmail.com> - 2013-03-20 07:40 +1100
Re: "javascript" Mike Duffy <Use.web.form@website_in_sig.com> - 2013-03-13 12:03 +0000
Re: "javascript" Dr J R Stockton <reply1300@merlyn.demon.co.uk.invalid> - 2013-03-14 21:22 +0000
Re: "javascript" Mike Duffy <Use.web.form@website_in_sig.com> - 2013-03-15 01:44 +0000
Re: "javascript" Dr J R Stockton <reply1300@merlyn.demon.co.uk.invalid> - 2013-03-16 19:42 +0000
Re: "javascript" Mike Duffy <Use.web.form@website_in_sig.com> - 2013-03-17 18:25 +0000
Re: "javascript" Tim Streater <timstreater@greenbee.net> - 2013-03-17 19:01 +0000
Re: "javascript" Gene Wirchenko <genew@telus.net> - 2013-03-15 10:55 -0700
Re: "javascript" John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-13 15:21 +0000
Re: "javascript" (was: OT: "javascript") Dr J R Stockton <reply1300@merlyn.demon.co.uk.invalid> - 2013-03-04 13:07 +0000
Re: "javascript" Christoph Becker <cmbecker69@gmx.de> - 2013-03-10 20:34 +0100
Re: "javascript" Tim Streater <timstreater@greenbee.net> - 2013-03-10 19:39 +0000
Re: OT: "javascript" was: Why is this returning NaN "J.R." <groups_jr-1@yahoo.com.br> - 2013-03-03 22:41 -0300
Re: OT: "javascript" was: Why is this returning NaN "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-03-04 09:57 +0100
Re: OT: "javascript" was: Why is this returning NaN Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-03-04 11:25 +0100
Re: OT: "javascript" was: Why is this returning NaN John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-04 14:52 +0000
Re: OT: "javascript" was: Why is this returning NaN Eric Bednarz <bednarz@fahr-zur-hoelle.org> - 2013-03-10 01:02 +0100
Re: OT: "javascript" was: Why is this returning NaN John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-10 10:52 +0000
Re: OT: "javascript" was: Why is this returning NaN Eric Bednarz <bednarz@fahr-zur-hoelle.org> - 2013-03-10 12:44 +0100
Re: OT: "javascript" was: Why is this returning NaN John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-10 17:49 +0000
Re: OT: "javascript" was: Why is this returning NaN Eric Bednarz <bednarz@fahr-zur-hoelle.org> - 2013-03-20 01:21 +0100
Re: OT: "javascript" was: Why is this returning NaN John G Harris <niam@jghnorth.org.uk.invalid> - 2013-03-20 15:25 +0000
Re: OT: "javascript" was: Why is this returning NaN Eric Bednarz <bednarz@fahr-zur-hoelle.org> - 2013-03-30 01:28 +0100
Re: Why is this returning NaN Tim Streater <timstreater@greenbee.net> - 2013-02-26 12:00 +0000
Re: Why is this returning NaN Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-02-26 18:07 +0100
Re: Why is this returning NaN Gregor Kofler <usenet@gregorkofler.com> - 2013-02-26 13:42 +0100
Re: Why is this returning NaN Dr J R Stockton <reply1300@merlyn.demon.co.uk.invalid> - 2013-02-27 20:43 +0000
Re: Why is this returning NaN "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-02-28 09:19 +0100
csiph-web