Regex(javascript), Debugger, Regex101

Question

I try to understand behavior of Regex101 debugger, This is the regex link, So if you activate the debugger and take a look from line 45, You can see the following behavior:

Line 45 the engine is watching the $ sign and understand that the end of the string haven't reached yet, So it need to subtract the string.
My problem is with lines (46,48,50,52,54), I try to understand why the engine is go from the $ sign (line 45) inside the subpattern(line 46) when the actual subtraction is done when the engine is on the $ sign, The way i see it is that 46,48,50,52,54 are wasted lines i can't understand their contribution, I mean why should i go inside the subpattern when the change happen when the engine on the $ sign to check if the string was end.

If anyone can help me with that i will be very thankful.

Update:

The regex:

<\/span>((?:(?!<\/span>)[\s\S])+)$

The string:

string</span>string</span>string</span>theStringIWant

I can't see that link with my outdated browser. Can you post the regex instead of people having to contend with an obstical. — user557597
– user557597, Commented Mar 5, 2014 at 19:50
I have seen several strange behaviours with regex101 debugger, I think that this debugger is buggy, It is better to test with regexbuddy. — Casimir et Hippolyte
– Casimir et Hippolyte, Commented Mar 5, 2014 at 20:34
Is there a free version for regexbuddy or similar software for free? — Aviel Fedida
– Aviel Fedida, Commented Mar 5, 2014 at 23:26
@CasimiretHippolyte: Whats wrong with my debugger? It does exactly what its supposed to. The lines mentioned by Aviel are lines where the engine is asserting positions for a continued match. The result you see on regex101 are 100% accurate. — Firas Dib
– Firas Dib, Commented May 9, 2014 at 9:59

Josh Crozier · Accepted Answer · 2015-12-12 02:35:47Z

1

Should work. Have you used the Raw regex at that web site?
There should be no options selected, ie: no multi-line or global or anything.

 #  Delimited:      /<\/span>((?:(?!<\/span>)[\s\S])+)$/
 #  Raw:             </span>((?:(?!</span>)[\s\S])+)$   

 </span>
 (
      (?:
           (?! </span> )
           [\s\S] 
      )+
 )
 $

Perl test case -

if ( "string</span>string</span>string</span>theStrngIWant" =~ /<\/span>((?:(?!<\/span>)[\s\S])+)$/)
{
    print "found: '$1'\n";
}

Output >>

found: 'theStrngIWant'

edited Dec 12, 2015 at 2:35

Josh Crozier

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answered Mar 5, 2014 at 20:03

user557597

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