Regular Expressions 101

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/
\b\d{2}\.\d{2}\.\d{4}\b
/
gm
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
\d
matches a digit (equivalent to [0-9])
{2} matches the previous token exactly 2 times
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
{2} matches the previous token exactly 2 times
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
{4} matches the previous token exactly 4 times
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gm

Test String