JavaScript Regex Cheatsheet

Core Syntax

Character Classes

• . any character except newline (or any with s flag)
• \d digit, \D non-digit
• \w word character, \W non-word
• \s whitespace, \S non-whitespace
• [abc] any of a, b, c · [^abc] none of them · [a-z] range

Quantifiers

• * zero or more · + one or more · ? optional
• {n} exactly n · {n,} n or more · {n,m} between n and m
• Add ? for lazy matching: .*? smallest match

Anchors

• ^ start of input (or line with m flag)
• $ end of input (or line with m flag)
• \b word boundary · \B non-boundary

Groups

• (abc) capturing group
• (?:abc) non-capturing group
• (?<name>abc) named group
• \1 backreference · $1, $<name> in replacement

Lookarounds

• (?=abc) positive lookahead
• (?!abc) negative lookahead
• (?<=abc) positive lookbehind
• (?<!abc) negative lookbehind

Flags

• g global · i case-insensitive · m multiline
• s dot matches newline · u Unicode · y sticky

Common Recipes

Email (loose)

/^[^\s@]+@[^\s@]+\.[^\s@]+$/

UUID v4

/^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i

ISO date (YYYY-MM-DD)

/^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01])$/

Slug (URL fragment)

/^[a-z0-9]+(?:-[a-z0-9]+)*$/

HEX color

/^#(?:[0-9a-f]{3}){1,2}$/i

Try It

Test any of these patterns in our free Regex Tester with live match highlighting and capture-group inspection.