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Re: Cannot manipulate array produced with string.match

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SteveYoungTbird wrote:

> On 06/27/2014 10:18 PM, SteveYoungTbird wrote:
>> On 06/27/2014 09:13 PM, Denis McMahon wrote:
>>> On Fri, 27 Jun 2014 20:00:18 +0200, SteveYoungTbird wrote:
>>>> I did as you  suggested and strangely the alert reads " 'jim' !== 'jim'
>>>> " as well as all of the other names not being equal to 'jim'
>>> Hmm, now you need to figure out what the differences are.
> 
> Got it! arr.match produces a string with a space after the comma.

s/arr/string/

> Therefore 'jim' in the loop was actually ' jim' and therefore didn't
> match,

It produces that because you have /(?:^| )/ in

>>>>>> var arr = [];
              ^^^^^[1][2]
>>>>>> arr = string.match(/(?:^| )([a-zäöüß]+)(?= [A-Z])/g);
                        [3]^^^^^^^^[4]-------^^^^^^^^^^^[5]

The /(?:…)/ only prevents capturing; it is _not_ a zero-length lookbehind 
(/(?<!…)/ would be, but it is not supported in ECMAScript as yet).

Many parts of this code do not make sense:

 [1] These languages use dynamic type-checking.  You do not need to
     initialize a variable that you will assign a reference to an Array
     instance with a reference to an Array instance.

 [2] No additional initialization is necessary.  String.prototype.match()
     always returns a reference to an Array instance if successful
     (otherwise “null” which overwrites the previous value anyway).

 [3] /(?:^| )…/g does not make sense, see above.

 [4] Capturing the sequence of word characters does not make sense with
     the global flag, as the resulting Array only contains the matches
     as primitive string values, if any.

 [5] /…(?= [A-Z])/g (zero-length positive lookahead) does not appear to
     make sense when you want to match/filter words.  Why would you only
     match words that precede a word starting with a capital letter?
     What about multiple spaces, tabs, and newlines?

In order to match words, simply match consecutive word characters (for the 
non-word characters delimit words and are not matched):

  var arr = string.match(/[a-zäöüß]+/ig);  

JSX:regexp.js can help there with basic support for Unicode character 
properties, like \p{L} for all letters.  But if you want to use .match() 
instead of .exec() then, you need to cast the String to a jsx.regexp.String:

  /* 
   * ["Über", "sprießende", "Äcker", "liefen", "zwölf", "Hühner",  
   *  "sagte", "der", "Bär", "in", "der", "Öffentlichkeit"]
   */
  new jsx.regexp.String(
    "Über sprießende Äcker liefen zwölf Hühner, sagte der Bär"
    + " in der Öffentlichkeit."
  ).match(new jsx.regexp.RegExp("\\p{L}+", "g"))

(You could say that this sentence – that just came to my mind – is an umlaut 
pangram, as a proof-of-concept.  It also features the sz ligature, used as 
in non-reformed Federal German spelling.)

See also:

  - <http://PointedEars.de/scripts/test/regexp>
  - <http://stackoverflow.com/a/8568325/855543>
  - My sig for the source code.

In order to filter out words, simply match on them or replace them.  There 
is no need for array iteration.

That said, Array.prototype.filter() (ES 5+) and equivalents are more 
efficient here than multiple Array.prototype.splice(), even though you 
cleverly iterate in reverse order so that the changed length does not 
matter.

Please post using your real name.

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | SVN: <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | ES Matrix: <http://PointedEars.de/es-matrix>
Please do not Cc: me. / Bitte keine Kopien per E-Mail.

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Thread

Cannot manipulate array produced with string.match SteveYoungTbird <stephen.young@chello.at> - 2014-06-27 09:17 +0200
  Re: Cannot manipulate array produced with string.match Denis McMahon <denismfmcmahon@gmail.com> - 2014-06-27 10:02 +0000
    Re: Cannot manipulate array produced with string.match SteveYoungTbird <stephen.young@chello.at> - 2014-06-27 20:00 +0200
      Re: Cannot manipulate array produced with string.match Denis McMahon <denismfmcmahon@gmail.com> - 2014-06-27 19:13 +0000
        Re: Cannot manipulate array produced with string.match SteveYoungTbird <stephen.young@chello.at> - 2014-06-27 22:18 +0200
          Re: Cannot manipulate array produced with string.match SteveYoungTbird <stephen.young@chello.at> - 2014-06-27 23:24 +0200
            Re: Cannot manipulate array produced with string.match Denis McMahon <denismfmcmahon@gmail.com> - 2014-06-28 01:07 +0000
              Re: Cannot manipulate array produced with string.match Denis McMahon <denismfmcmahon@gmail.com> - 2014-06-28 01:16 +0000
            Re: Cannot manipulate array produced with string.match Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-06-28 23:53 +0200
              Re: Cannot manipulate array produced with string.match SteveYoungTbird <stephen.young@chello.at> - 2014-06-29 22:24 +0200
                Re: Cannot manipulate array produced with string.match Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-06-29 23:19 +0200
  Re: Cannot manipulate array produced with string.match JJ <jj4public@vfemail.net> - 2014-06-27 19:31 +0700

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