Regular Expressions 101

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/
(?=<[^<]*[\s]+title="([^"]*)")|<\s*a\s+[^<]*>([^<]*)([^<]*)
/
g
1st Alternative
(?=<[^<]*[\s]+title="([^"]*)")
Positive Lookahead
(?=<[^<]*[\s]+title="([^"]*)")
Assert that the Regex below matches
< matches the character < with index 6010 (3C16 or 748) literally (case sensitive)
Match a single character not present in the list below
[^<]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
< matches the character < with index 6010 (3C16 or 748) literally (case sensitive)
Match a single character present in the list below
[\s]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
\s matches any whitespace character (equivalent to [\r\n\t\f\v ])
title="
matches the characters title=" literally (case sensitive)
1st Capturing Group
([^"]*)
Match a single character not present in the list below
[^"]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
" matches the character " with index 3410 (2216 or 428) literally (case sensitive)
" matches the character " with index 3410 (2216 or 428) literally (case sensitive)
2nd Alternative
<\s*a\s+[^<]*>([^<]*)([^<]*)
< matches the character < with index 6010 (3C16 or 748) literally (case sensitive)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
a matches the character a with index 9710 (6116 or 1418) literally (case sensitive)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
Match a single character not present in the list below
[^<]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
< matches the character < with index 6010 (3C16 or 748) literally (case sensitive)
> matches the character > with index 6210 (3E16 or 768) literally (case sensitive)
2nd Capturing Group
([^<]*)
Match a single character not present in the list below
[^<]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
< matches the character < with index 6010 (3C16 or 748) literally (case sensitive)
3rd Capturing Group
([^<]*)
Match a single character not present in the list below
[^<]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
< matches the character < with index 6010 (3C16 or 748) literally (case sensitive)
Global pattern flags
g modifier: global. All matches (don't return after first match)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
g

Test String