Groups > comp.lang.javascript > #20313

Identifying a regex

From	Stefan Weiss <krewecherl@gmail.com>
Newsgroups	comp.lang.javascript
Subject	Identifying a regex
Date	2013-06-17 01:47 +0200
Organization	albasani.net
Message-ID	<kplir9$pj9$1@news.albasani.net> (permalink)

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What do you think is the best way to identify a value as a regular
expression (reference to a RegExp object)? I can see at least four
different ways, each with its own drawbacks:

  A) val instanceof RegExp
  B) val.constructor.name == "RegExp"
  C) Object.prototype.toString.call(val) == "[object RegExp]"
  D) duck typing


A selection of possible error sources:

A) Has problems when the regex object was created in a different window
(frame) from where it's being analyzed.

B) The constructor property can be changed manually at any time.

C) I've seen mention of failures in IE when the regex is created in
another window (frame). Theoretically, a badly designed host object
could also have an internal [[Class]] of "RegExp" and still be compliant
with the standard, which only covers the [[Class]] names of native objects.

D) It's probably a duck, but it might be a confused goose.


I'm currently favoring option (B). The way I see it, if somebody messes
around with the constructor property of a native object for no good
reason, they're voiding their warranty. In addition, this test is not
intended to be part of a general purpose library, which means that the
number of potentially misbehaving users is very limited.

Option (C) also looks promising, if the IE problem only affects older
versions. Unfortunately, I can't test this, because my memory is maxed
again and I can't launch any more VMs. I seriously need to upgrade...

Looking forward to your thoughts about this.

- stefan

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Thread

Identifying a regex Stefan Weiss <krewecherl@gmail.com> - 2013-06-17 01:47 +0200
  Re: Identifying a regex "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2013-06-16 19:30 -0700
    Re: Identifying a regex Stefan Weiss <krewecherl@gmail.com> - 2013-06-17 14:05 +0200
      Re: Identifying a regex "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2013-06-17 16:16 -0700
        Re: Identifying a regex Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-06-18 02:13 +0200
          Re: Identifying a regex Stefan Weiss <krewecherl@gmail.com> - 2013-06-18 20:14 +0200
            Re: Identifying a regex Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-06-18 21:39 +0200
              Re: Identifying a regex Stefan Weiss <krewecherl@gmail.com> - 2013-06-18 23:58 +0200
                Re: Identifying a regex Stefan Weiss <krewecherl@gmail.com> - 2013-06-25 22:05 +0200
                Re: Identifying a regex "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2013-06-25 16:59 -0700
                Re: Identifying a regex Stefan Weiss <krewecherl@gmail.com> - 2013-06-26 23:47 +0200
              Re: Identifying a regex Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-06-23 20:01 +0200
        Re: Identifying a regex "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2013-06-18 00:40 -0700
          Re: Identifying a regex Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-06-18 10:39 +0200
            Re: Identifying a regex "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2013-06-18 19:32 -0700
              Re: Identifying a regex Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-06-19 14:05 +0200
                Re: Identifying a regex "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2013-06-19 20:24 -0700
                Re: Identifying a regex Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-06-20 12:27 +0200
                Re: Identifying a regex "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2013-06-20 18:08 -0700
  Re: Identifying a regex JJ <duh@nah.meh> - 2013-06-17 13:58 +0700
    Re: Identifying a regex Stefan Weiss <krewecherl@gmail.com> - 2013-06-17 14:11 +0200
      Re: Identifying a regex JJ <duh@nah.meh> - 2013-06-18 12:46 +0700
        Re: Identifying a regex Stefan Weiss <krewecherl@gmail.com> - 2013-06-18 20:17 +0200
  Re: Identifying a regex Andreas Bergmaier <andber93@web.de> - 2013-06-18 21:14 +0200

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