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Message-ID: <12786665.ZbpLptdNGN@PointedEars.de>
From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Reply-To: Thomas 'PointedEars' Lahn <usenet@PointedEars.de>
Organization: PointedEars Software (PES)
Date: Fri, 03 May 2013 01:26:51 +0200
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Subject: Re: About keeping my array 1 based after having sorted it
Newsgroups: comp.lang.javascript
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Scott Sauyet wrote:

> You can probably achieve the same thing with this:
> 
>     bookingArray.sort(function(a, b) {
>       return a.Objectid < b.Objectid ? -1 :
>              a.Objectid > b.Objectid ? +1 :
>              new Date(a.Fromtime) - new Date(b.Fromtime);

(The “+” in “+1” is a superfluous conversion operation; it is *not* a no-op.  
Also, few people know that “-1” actually is a “unary -” conversion operation 
on the primitive Number value 1.  See ES 5.1, §§ 11.4.6 and 11.4.7.)

Please do not write or suggest such code; it is a maintenance nightmare.  
Write such code if you want your colleagues to dislike you for it, put 
politely.  See also: <http://stackoverflow.com/q/14693135/855543>

The least you should do is using parentheses to group the expressions to 
make it easier to read and to debug, for example (preferred by me)

      return (a.Objectid < b.Objectid
        ? -1
        : (a.Objectid > b.Objectid
            ? 1
            : new Date(a.Fromtime) - new Date(b.Fromtime)));

or (preferred by others)

      return (a.Objectid < b.Objectid)
        ? -1
        : (a.Objectid > b.Objectid)
            ? 1
            : new Date(a.Fromtime) - new Date(b.Fromtime);

As the conversion to Date appears to be superfluous here¹, there is also 

  var comparator = jsx.array.getComparator(
    ["Objectid", "Fromtime"], {numeric: true});

  bookingArray.sort(comparator);

(see 
<http://PointedEars.de/websvn/filedetails.php?repname=JSX&path=/trunk/array.js>)

The least you should do is cache the comparator.

>     });
> 
> And if the Objectid properties are numeric, you can get even simpler:
> 
> 
>     bookingArray.sort(function(a, b) {
>       return a.Objectid - b.Objectid ||
>              new Date(a.Fromtime) - new Date(b.Fromtime);
>     });

Again, indicating the operator precedence is a good idea:

    bookingArray.sort(function (a, b) {
      return (a.Objectid - b.Objectid)
        || (new Date(a.Fromtime) - new Date(b.Fromtime));
    });

or (more efficient here)

    bookingArray.sort(function (a, b) {
      return (a.Objectid - b.Objectid) || (a.Fromtime - b.Fromtime);
    });

It should also be noted that using the “||” operator carries with it the 
internal conversion of the first operand to Boolean which may be more 
expensive than other approaches.

______
¹  However, this gives me the idea that it could be useful that
   jsx.array.getComparator() could also be passed a callback or constructor
   for each key, or all keys, whose return value would be used as operand
   in the comparison.  What do you think?
-- 
PointedEars

Twitter: @PointedEars2
Please do not Cc: me. / Bitte keine Kopien per E-Mail.