RegEx Reference

1. Tools
2. Cheatsheet
3. Examples
4. Programming Languages

Tools

1. Online Tool

2. grep -P "<regex>" <path> # omit leading & trailing '/' from regex

3. sag "<regex>" <path> # omit leading & trailing '/' from regex

4. VS Code: Ctrl+F > Alt+R

Cheatsheet

Common

RegEx	Description
.	Any Character Except New Line
\d	Digit (0-9)
\D	Not a Digit (0-9)
\w	Word Character (a-z, A-Z, 0-9, _)
\W	Not a Word Character
\s	Whitespace (space, tab, newline)
\S	Not Whitespace (space, tab, newline)
\b	Word Boundary
\B	Not a Word Boundary
^	Beginning of a String
$	End of a String
[]	Matches Characters in brackets
[^ ]	Matches Characters NOT in brackets
( )	Either Or Group

Quantifiers

RegEx	Description
*	0 or More
+	1 or More
?	0 or One
{3}	Exact Number
{3,4}	Range of Numbers (Minimum, Maximum)

Examples

Exact Match

ninja       # 'ninja'
^ninja$     # exactly 'ninja' and nothing else

Character Set

[ng]inja    # 'ninja' or 'ginja'
ninja[1-9]  # 'ninja1' to 'ninja9'
[^n]inja    # every '_inja' except 'ninja'

Multiple Characters

[0-9]+          # multiple digits
a{3}            # 3 'a's
[a-zA-Z]{5,8}   # 5 to 8 characters

Optional/Alternate Matches

(cat|dog|bird)  # 'cat' or 'dog' or 'bird'
M(r|s|rs)\.?    # 'Mr/Mr./Ms/Ms./Mrs/Mrs.'

Programming Languages

JavaScript

// these two are equivalent
const reg1 = /[a-z]/i
const reg2 = new RegExp(/[a-z]/, 'i')

reg1.test("b")  // true
reg2.test("3")  // false

Matching Groups

const text = "http://www.google.com";
const regex = /https?://(www\.)?(\w+)(\.\w+)/
const [whole, www, domain, extension] = text.match(regex)