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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: Sat, 26 Sep 2015 14:43:22 +0200
Organization: PointedEars Software (PES)
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Ben Bacarisse wrote:

> jonas.thornvall@gmail.com writes:
>> Den lördag 26 september 2015 kl. 00:11:31 UTC+2 skrev Danny:
>>> in short, if the value is an integer, it will never return NaN.
>>> What if may be happening in your case, is that the object gets
>>> something else other than a numeric value.
>>> 
>>> but a solution depends on what the context for all that is
>>> and you haven't given us context or relevant code of the matter
>>
>> Well sometimes the index of the array is empty for the leading
>> position, it is an carry operation.

It is not the index that is "empty" then, but the array element.  The index 
is a number used for addressing the elements of an array instead.

> As yet unassigned positions in an array are undefined but the isNaN
> function returned true for undefined values.  It's likely that you don't
> have a numeric NaN in addOne[i], but undefined instead.

The Number.isNaN() method of ECMAScript Ed. 6 can solve this problem.
It can be emulated as follows:

  if (typeof Number.isNaN != "function")
  {
    Number.isNaN = function (value) {
      return (typeof value == "number") && (value != value);
    };
  }

This makes use of the fact that the IEEE 754 “Not-a-number” value is the 
only Number value that is not equal to itself by definition.

See also, and compare: 
<https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Number/isNaN>
 

PointedEars
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