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From: Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups: comp.lang.javascript
Subject: Re: function to get frequencies of a char array
Date: Tue, 27 Jan 2015 01:37:21 +0000
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Thomas 'PointedEars' Lahn <PointedEars@web.de> writes:

> 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").

Isn't

  if (a.hasOwnProperty(i)) { counts[e] ? ++counts[e] : (counts[e] = 1); }

a better way to deal with sparse arrays in such a loop?  Testing e seems
rather heavy-handed, though it's not clear what the OP might want in
anything but the simple case given.  In a general counting loop one
would probably want to count zeros and NaNs and so on.

<snip>
-- 
Ben.