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Re: function to get frequencies of a char array

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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
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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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