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JavaScript RegExp Classes

A character class matches one character from a set of allowed characters. "Any vowel," "any digit," "any letter from a to f": classes are how a single position in a pattern can accept more than one thing.

// Square Brackets: Your Own Set

/[aeiou]/         // any one vowel
/gr[ae]y/         // "gray" or "grey"
/[0-9]/           // any one digit (a range)
/[a-z]/           // any lowercase letter
/[A-Za-z0-9]/     // any letter or digit (ranges combine)
"grey gray groy".match(/gr[ae]y/g)    // ["grey", "gray"]
"Banana".match(/[aeiou]/gi).length   // 3 vowels
["grey", "gray"] 3
One Character
However long the list inside the brackets, a class matches exactly one character. [abc] matches "a" or "b" or "c", never "abc". To match several in a row you add a quantifier (covered in RegExp Quantifiers): [abc]+.

// Negated Classes: Anything Except

A ^ right after the opening bracket flips the meaning:

/[^aeiou]/     // any character that is NOT a vowel
/[^0-9]/       // any non-digit

"h3ll0 w0rld".replace(/[^a-z ]/g, "*")   // "h*ll* w*rld"
h*ll* w*rld

// More Class Examples

console.log("Hello World!".match(/[HW]/g));
console.log("This is W3School".match(/[A-Z]/g));
console.log("123456789".match(/[1-4]/g));    // same as [1234]
console.log("abcdef".match(/[^a-c]/g));       // NOT a, b, or c
["H", "W"] ["T", "W", "S"] ["1", "2", "3", "4"] ["d", "e", "f"]

A range is a shortcut for listing: [0-4] is the same as [01234], and [a-e] is the same as [abcde].

W3Schools wording
W3Schools' table says [abc] "matches all characters between the brackets." It matches any one of them per position. "abc".match(/[abc]/)[0] is "a", not "abc".

// Shorthand Classes

These come up so often they have built-in shortcuts:

Class Matches Same as
\dDigit[0-9]
\w"Word" character[A-Za-z0-9_]
\sWhitespacespace, tab, line break...
\D \W \SThe opposite of each (capital = NOT)[^0-9] etc.
.Any character except a line break
 
"Room 4B, floor 12".match(/\d/g)      // ["4", "1", "2"]
"a  b\tc".split(/\s+/)              // ["a", "b", "c"]
"x_1-y@2".match(/\W/g)              // ["-", "@"]
["4", "1", "2"] ["a", "b", "c"] ["-", "@"]
Watch out
\w only knows English letters. It does not match accented letters like "é" or "ñ". "café".match(/\w+/)[0] is "caf". For real-world names and words, use the Unicode classes below.

// Unicode Property Classes

With the u flag, \p{...} matches characters by category, in every language:

"café naïve".match(/\p{L}+/gu)    // ["café", "naïve"]   \p{L} = any letter
"Straße".match(/\p{Lu}/gu)          // ["S"]   \p{Lu} = uppercase letter
"Hi 👋 there 🎉".match(/\p{Emoji_Presentation}/gu)   // ["👋", "🎉"]
["café", "naïve"] ["S"] ["👋", "🎉"]

// Special Characters Inside Brackets

Inside square brackets most symbols lose their special meaning. Only a few need care:

/[.?!]/        // a period, question mark, or exclamation point (no escaping needed)
/[-+]/         // a hyphen FIRST or LAST is literal
/[a\-z]/       // escaped hyphen: "a", "-", or "z" (not a range)
/[\]]/         // a closing bracket must be escaped

// Putting It Together

// A simple product code: 3 capital letters, a dash, 4 digits
const code = /^[A-Z][A-Z][A-Z]-\d\d\d\d$/;

code.test("ABC-1234")   // true
code.test("abc-1234")   // false
code.test("AB-12345")   // false
true false false

Writing [A-Z] three times works but is repetitive. Quantifiers (later) shorten it to [A-Z]{3}.

// Quick Check

What does this log?

console.log("B2B for 4U".match(/[A-Z0-9]/g).join(""));
Show answer
B2B4U. The class matches one capital letter or digit at a time, in the order they appear. Lowercase letters and spaces are skipped.

Which one matches "grey" and "gray" but not "groy"?

  1. /gr.y/
  2. /gr[ae]y/
  3. /gr[^ae]y/
  4. /gr[a-z]y/
Show answer
B. A allows any character (including o). C allows everything except a and e. D allows any lowercase letter, including o.

Why does "José".match(/\w+/)[0] give "Jos"?

  1. \w skips capital letters
  2. \w only knows A-Z, a-z, 0-9, and _
  3. The + stops after 3 characters
  4. match drops the last character
Show answer
B. Use /\p{L}+/u to match letters in any language.

// Try It

  1. Click Open Playground. Count the consonants in the sentence with a negated class
  2. Split a messy string with mixed spaces, tabs, and newlines using \s+
  3. Compare \w+ and \p{L}+ (with the u flag) on "Zoë and Ángel"
  4. Write a pattern for a time like "09:45" using only classes
// Video Walkthroughs
Last updated: Oct 10, 2026, 1:46 AM ET