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Message-ID: <4497153.IWULeidUyA@PointedEars.de>
From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Reply-To: Thomas 'PointedEars' Lahn <usenet@PointedEars.de>
Organization: PointedEars Software (PES)
Date: Tue, 18 Jun 2013 21:39:49 +0200
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Subject: Re: Identifying a regex
Newsgroups: comp.lang.javascript
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Stefan Weiss wrote:

> On 2013-06-18 02:13, Thomas 'PointedEars' Lahn wrote:
>> In the case of references to RegExp instances, though, where inheriting
>> from their prototype does not make sense and so all pertinent objects
>> have [[Class]] "RegExp", in JSX:regexp.js I have switched from comparison
>> [[against the “constructor” property value to jsx.object.getClass() for
>> the next revision, for cross-view referencing.
> 
> For reference:
> 
>   var _getClass = (function () {
>     var _toString = ({}).toString;
> 
>     return function (obj) {
>       return (_toString.call(obj)
>         .match(/^\s*\[object\s+(\S+)\s*\]\s*$/) || [, ])[1];
>     };
>   }());
> 
> 
http://pointedears.de/websvn/filedetails.php?repname=JSX&path=%2Ftrunk%2Fobject.js
> 
> That would correspond to option (C) in my original question.

Yes.
 
> The old comparison method in your regexp.js (rev 361) is not the same as
> option (B), however: comparing the constructor property directly with
> RegExp does not work across frames, but comparing constructor.name with
> "RegExp" does (as long as nobody messed with the constructor directly).

I am not convinced that constructor.name is interoperable in the first 
place.  The ECMAScript Support Matrix, Version 2, contains a testcase for 
Function.prototype.name that has been recently run (by someone else – thank 
you) to fail in JavaScript 1.8.6 and JScript 10.0.16578.  But that might be 
due to “name” being a property of Function instances only in those 
implementations.  I shall modify that testcase accordingly.

<http://PointedEars.de/es-matrix/?filter=Function.prototype.name#features-table>

That said, neither Function.prototype.name nor functionInstance.name are 
specified in the ECMAScript Language Specification, 5.1 Edition, §15.3, so 
they are very likely not interoperable.  Which is why there is

/**
 * Returns the name of a function
 *
 * @param {Function|String} aFunction
 * @return {string}
 *   The name of a function if it has one; the empty string otherwise.
 */
jsx.object.getFunctionName = function (aFunction) {
  /* Return the empty string for null or undefined */
  return (aFunction != null
           && typeof aFunction.name != "undefined" && aFunction.name)
    || (String(aFunction).match(/\s*function\s+([A-Za-z_]\w*)/) || [, ""])
[1];
};
 
> In my specific case, I can see both methods working equally well.  […]

I don't.

-- 
PointedEars

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