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Luna Tech: Regex Tutorial for Everyone

Note: For a better reading experience, please open this link in a computer browser, the mobile view really messed up the formatting, especially the tables.

1. Metacharacters

Metacharacter	Meaning
/	The start/end of the regex e.g., /pattern/
\	Escape from special meaning e.g., /0\.9/
.	Wildcard metacharacter, matches any character except newline e.g., /0.9/
*	item before appear 0 or more times e.g., /a*/
+	item before appear 1 or more times e.g., /a+/
?	item before appear 0 or 1 time e.g., /a?/
-	Defines a character range e.g., /[0-9]/
pipe	Alternation (OR)
{ }	Quantified Repetition e.g., /a{3,5}/
[ ]	Defines a Character Set e.g., /[aeiou]/
( )	Defines a group e.g., /(group1)-(group2)/
^	1. When used at the start of a character set, defines a negative set. e.g., /[^aeiou]/ 2. When used at the start of Regex, means the start of string/line. e.g., /^Banana/
$	End of string/line e.g., /Banana$/
\A	Start of string, not end of line e.g., /\ABanana/ JS engine not support
\Z	End of string, not end of line e.g., /Banana\Z/ JS engine not support
\b	Word boundary (start/end of a word) e.g., /\bApple\b/
\B	Not a word boundary e.g., /\Bea\B/

Note:

| cannot be correctly rendered in the markdown table above, so I use pipe for alternation.

e.g., /match1|match2|match3)/

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2. Special Characters

Special Character	Meaning
\t	Tab
\r	Newline, CR (Short for Carriage Return) It just means to end the current line, not to start a new line.
\n	Newline, LF (Short for Line Feed) Unix and Linux use this to represent an enter keypress
\r\n	Newline, CRLF (Short for Carriage Return + Line Feed) Windows uses this to represent an enter keypress

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3. Character ranges

Character ranges	Explanation
[0-9]	Match any number between 0 and 9
[A-Z]	Match any uppercase characters from A to Z
[a-z]	Match any lowercase characters from a to z
[A-Za-z]	Match any character from a to z, case insensitive
[a-f]	Match any lowercase character from a to f This is an example of how you can use the range to customize your needs.

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4. Shorthand character sets

Shorthand	Character Set	Explanation
\d	[0-9]	Digit
\w	[a-zA-Z0-9_]	Word Character (include _ but exclude -)
\s	[ \t\r\n]	Whitespace
\D	[^0-9]	Not a digit
\W	[^a-zA-Z0-9_]	Not a word character (exclude _ but include -)
\S	[^ \t\r\n]	Not a whitespace