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Regex match

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  Regex match andrew.perrins@gmail.com - 2013-08-05 14:16 -0700
    Re: Regex match "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-08-05 23:45 +0200
    Re: Regex match Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-08-05 22:45 +0100

#20870 — Regex match

This is not strictly a js question, but I'm hoping I might get some feedback.

Succinctly, my question is, why does this provide a match:

 'D123'.match(/\d+/);  // -> result is ["123"]

whereas this does not provide a match:

 'D123'.match(/\d*/)   // -> [""]


If I add the "global" flag on the second regex, it's true, I get the same result as one of the matches.  But I'd expect that, since the "+" and "*" are both greedy, that they should each return the string of digits as a result with no flags.

Any help appreciated; thanks.

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#20871

 wrote on 05 aug 2013 in comp.lang.javascript:

> Succinctly, my question is, why does this provide a match:
> 
>  'D123'.match(/\d+/);  // -> result is ["123"]
> 
> whereas this does not provide a match:
> 
>  'D123'.match(/\d*/)   // -> [""]

Oh, but it DOES provide a match!!!!

The first match of \d* 
is the empty string section in front of the 'D'.

This will explain it to you:

alert( 'D123'.replace(/\d+/,'x') ); // Dx

and

alert( 'D123'.replace(/\d*/,'x') ); // xD123




-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

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#20872

andrew.perrins@gmail.com writes:

> This is not strictly a js question, but I'm hoping I might get some feedback.
>
> Succinctly, my question is, why does this provide a match:
>
>  'D123'.match(/\d+/);  // -> result is ["123"]
>
> whereas this does not provide a match:
>
>  'D123'.match(/\d*/)   // -> [""]

That looks like a match to me (and a correct one at that).

> If I add the "global" flag on the second regex, it's true, I get the
> same result as one of the matches.  But I'd expect that, since the "+"
> and "*" are both greedy, that they should each return the string of
> digits as a result with no flags.

Being greedy does not mean "skip over a short match to find a longer
one".  Here, \d* matches zero character right off the mark, and that's
the match you get.  Making the match global gives you all the others.

-- 
Ben.

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