Regular Expressions 101

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/
(^\/.*)?(\/$|\/(\?.*))
/
gm
1st Capturing Group
(^\/.*)?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
^ asserts position at start of a line
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
2nd Capturing Group
(\/$|\/(\?.*))
1st Alternative
\/$
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
$ asserts position at the end of a line
2nd Alternative
\/(\?.*)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
3rd Capturing Group
(\?.*)
\? matches the character ? with index 6310 (3F16 or 778) literally (case sensitive)
.
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)
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.

Regular Expression
No Match

/
/
gm

Test String

Code Generator

Generated Code

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Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report.
For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions