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Groups > comp.lang.javascript > #26720
| From | Thomas 'PointedEars' Lahn <PointedEars@web.de> |
|---|---|
| Newsgroups | comp.lang.javascript |
| Subject | Re: function to get frequencies of a char array |
| Date | 2015-01-27 01:00 +0100 |
| Organization | PointedEars Software (PES) |
| Message-ID | <4289032.9WYFBcEGMJ@PointedEars.de> (permalink) |
| References | (2 earlier) <m9ti7r$sbg$1@solani.org> <26839541.MRbOrngyXZ@PointedEars.de> <87twzgl0aq.fsf@bsb.me.uk> <2697158.aGRKFDBAEn@PointedEars.de> <87lhkskr0r.fsf@bsb.me.uk> |
Ben Bacarisse wrote:
> Thomas 'PointedEars' Lahn <PointedEars@web.de> writes:
>> Ben Bacarisse wrote:
>>> Thomas 'PointedEars' Lahn <PointedEars@web.de> writes:
>>>> var counts = {};
>>>>
>>>> for (var i = 0, len = a.length; i < len; ++i)
>>>> {
>>>> /* NOTE: hasOwnProperty() may be required */
>>>> var e = a[i];
>>>> e ? ++counts[e] : (counts[e] = 1);
>>>> }
>>>
>>> I think you meant counts[e] ? ++counts[e] : (counts[e] = 1); here (and
>>> immediately below): […]
>>
>> No, but
>>
>> if (e) { counts[e] ? ++counts[e] : (counts[e] = 1); }
>
> Why?
Because there are sparse arrays ([To]String(“undefined”) === "undefined").
Your variant suffices for sparse arrays iterated over with the “for–in”
statement, provided that there are no other inherited or own enumerable
properties (otherwise .hasOwnProperty() needs to be used and the property
name needs to be checked against the specification for Array indexes).
> And did you mean to add the if (e) test to the forEach examples, too?
No, Array.prototype.forEach() already tests internally if the numeric
property name is an index. That is also the reason why it is so very
inefficient with sufficiently sparse large arrays.
--
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.
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function to get frequencies of a char array JRough <janis.rough@gmail.com> - 2015-01-22 14:43 -0800
Re: function to get frequencies of a char array Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-01-22 23:09 +0000
Re: function to get frequencies of a char array JRough <janis.rough@gmail.com> - 2015-01-22 15:22 -0800
Re: function to get frequencies of a char array JRough <janis.rough@gmail.com> - 2015-01-22 15:23 -0800
Re: function to get frequencies of a char array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-01-23 00:36 +0100
Re: function to get frequencies of a char array "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-01-23 14:27 +0100
Re: function to get frequencies of a char array Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-23 16:52 +0100
Re: function to get frequencies of a char array Scott Sauyet <scott.sauyet@gmail.com> - 2015-01-23 09:03 -0800
Re: function to get frequencies of a char array "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-01-23 23:03 +0100
Re: function to get frequencies of a char array Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-01-24 14:29 +0000
Re: function to get frequencies of a char array Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-24 15:36 +0100
Re: function to get frequencies of a char array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-01-24 16:06 +0100
Re: function to get frequencies of a char array "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-01-24 18:05 +0100
Re: function to get frequencies of a char array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-01-26 10:21 +0100
Re: function to get frequencies of a char array "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-01-26 13:22 +0100
Re: function to get frequencies of a char array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-01-26 15:50 +0100
Re: function to get frequencies of a char array "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-01-26 20:48 +0100
Re: function to get frequencies of a char array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-01-26 23:08 +0100
Re: function to get frequencies of a char array Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-27 01:05 +0100
Re: function to get frequencies of a char array "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-01-27 13:55 +0100
Re: function to get frequencies of a char array Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-27 14:50 +0100
Re: function to get frequencies of a char array "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-01-27 19:35 +0100
Re: function to get frequencies of a char array Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-27 22:15 +0100
Re: function to get frequencies of a char array "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-01-31 00:40 +0100
Re: function to get frequencies of a char array Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-01-24 17:49 +0000
Re: function to get frequencies of a char array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-01-26 10:23 +0100
Re: function to get frequencies of a char array Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-27 01:00 +0100
Re: function to get frequencies of a char array Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-01-27 01:37 +0000
Re: function to get frequencies of a char array Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-27 03:03 +0100
Re: function to get frequencies of a char array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-01-23 15:29 +0100
Re: function to get frequencies of a char array Denis McMahon <denismfmcmahon@gmail.com> - 2015-01-23 02:16 +0000
Re: function to get frequencies of a char array Denis McMahon <denismfmcmahon@gmail.com> - 2015-01-23 02:18 +0000
Re: function to get frequencies of a char array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-01-23 09:06 +0100
Re: function to get frequencies of a char array Stefan Weiss <krewecherl@gmail.com> - 2015-01-23 09:53 +0100
Re: function to get frequencies of a char array "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-01-23 13:37 +0100
Re: function to get frequencies of a char array "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-01-23 13:49 +0100
Re: function to get frequencies of a char array "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-01-23 13:31 +0100
Re: function to get frequencies of a char array Denis McMahon <denismfmcmahon@gmail.com> - 2015-01-23 14:49 +0000
Re: function to get frequencies of a char array Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-23 17:09 +0100
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