Regular Expressions 101

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Community Patterns

107

ECMAScript/JavaScript trim

ECMAScript (JavaScript)
Trim leading and trailing whitespace from a string.
Submitted by fp - 11 years ago (Last modified 3 months ago)
238

Matching email addresses per RFC5322

PCRE (PHP <7.3)
The BNF rules from RFC 5322 transformed to PCRE by Nikita Popov and described in the post http://nikic.github.io/2012/06/15/The-true-power-of-regular-expressions.html.
Submitted by Michael Musson - 11 years ago
483

regex101.com permalink id grabber

PCRE (PHP <7.3)
Grabs the ID for the regex101.com permalink code. If a revision number is provided, grab that as well.
Submitted by chris mccoy - 11 years ago (Last modified 8 months ago)
1...900901902

Community Library Entry

2

Regular Expression
PCRE2 (PHP >=7.3)

/
(?=(\b\w{4,}\b)(?:.*\b\1\b){2})(?!(\b\w{4,}\b)(?:.*\b\1\b){3})
/
gi
Open regex in editor

Description

I'd like to know if a text contains words with 4 characters or more which are repeated 3 or more times in the text (anywhere in the text).

If so, set one (and only one) backreference for each word.

Submitted by anonymous - 2 months ago