Regular Expressions 101

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/
^.(?<!JJ|M3)$
/
gm
^ asserts position at start of a line
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Negative Lookbehind
(?<!JJ|M3)
Assert that the Regex below does not match
1st Alternative
JJ
JJ matches the characters JJ literally (case sensitive)
2nd Alternative
M3
M3 matches the characters M3 literally (case sensitive)
$ asserts position at the end of a line
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

Regular Expressions 101

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