RegEx

Notes for RegEx respectively Regular Expressions and also some useful ressources.

General Rules

Character Types

Type	Example
Literal	a b c 1 2 3
Meta characters	. [[ ] { } ? * + | ( ) ^ $

Meta Characters

Meta Character	Example
Single Character	.
Character class digit	\d
Character class character	\w
Character class whitespace (Space, tab, new line, carriage return)	\s
Inversion of character classes (Not)	\D, \W, \S
Word and text boundaries	b ^ $

Ranges and Groups

Range or Group	Example
Character class range	[a-c]
Inversion of character class range	[^abc]
Grouping with alternatives	(Mon|Tues)day

Quantifiers

Quantifier	Example
Zero or one character	?
Zero or more characters (Kleene Star)	*
One or more characters (Kleene Plus)	+
Three characters	{3}
Four to 20 characters	{4,20}

White Space Characters

White Space	Example
Space	_
Tab	\t
New line	\n
Carriage return	\r
Any white space character	\s

Line start and end

Type	Example
Start of line	^
End of line	$

Groups and nested groups

Type	String	Expression	Results
Group Example 1	IMG1000.png	^(IMG\d+\.png)$	IMG1000.png
Group Example 2	IMG1000.png	^(IMG\d+)\.png$	IMG1000
Nested group	IMG1000.png	^(IMG(\d+))\.png$	Group 1: IMG1000 Group 2: 1000
Multiple groups	1920x1080	(\d+)x(\d+)	Group 1: IMG1000 Group 2: 1000

Online Regex Tools

• https://regexr.com/
• https://regex101.com/

Tutorials and Guides

Guide (german): https://t3n.de/news/regex-guide-t3n-552858/

Quick Start Cheat Sheet: https://www.rexegg.com/regex-quickstart.html

Advanced tutorial: https://www.rexegg.com/regex-disambiguation.html

Practical tutorial: https://regexone.com/

Regex with JavaScript: https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/#regular-expressions