Regular Expressions 101

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/
(?=\[)()(?=.\])
/
gm
Positive Lookahead
(?=\[)
Assert that the Regex below matches
\[
matches the character [ literally (case sensitive)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
1st Capturing Group
()
matches the character literally (case sensitive)
Positive Lookahead
(?=.\])
Assert that the Regex below matches
.
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)
\] matches the character ] literally (case sensitive)
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