\w?\w matches one word character: ASCII letters (A–Z, a–z), digits (0–9), or underscore (_). It is shorthand for [A-Za-z0-9_].
\w → letter, digit, or underscore
\W → anything else (opposite)
/\w/.test("!") → false
/\w/.test("a") → true
/\w/.test("_") → true
"hi_42!".match(/\w+/g) → ["hi_42"]| Use | Prefer |
|---|---|
| Detect a word char | /\w/ |
| Extract tokens | str.match(/\w+/g) |
| Validate identifier | /^\w+$/ |
| Opposite class | \W |
\wMatch one character, or add + when a whole token matters.
/\w/ to ask “is there any word character?”+ for runs: /\w+/ matches identifiers and words.match(/\w+/g) to extract every token./^\w+$/ to require the whole string to be word characters only.| Piece | Required? | Role |
|---|---|---|
\w in the pattern | Yes | Match one word character |
+ / * / {n,m} | Optional | Match longer tokens |
^ … $ | Optional | Validate the entire string |
| Inverse | — | \W matches non-word characters |
pattern has "\w"
read next character ch from the string
if ch is A–Z, a–z, 0–9, or "_":
accept match
else:
fail this path
common actions:
test(str) → true if any word char exists
match(/\w+/g) → list of word tokens
/^\w+$/.test(str) → whole string is alphanumeric/_Keep these patterns handy for identifiers and tokens.
| Topic | Detail |
|---|---|
| Matches | [A-Za-z0-9_] |
| One character | \w |
| Token / word | \w+ |
| Extract all | match(/\w+/g) |
| Validate | /^\w+$/ |
| Opposite | \W |
| Standard | ES3+ (universal) |
Run common \w operations on sample strings with letters, digits, and symbols.
Short, copy-ready snippets. Open DevTools Console, or use Try It Yourself for a live editor.
Return true when a letter, digit, or underscore appears.
console.log(/\w/.test("!!!")); // false
console.log(/\w/.test("a")); // true
console.log(/\w/.test("_")); // true
console.log(/\w/.test("9")); // true"!" is not a word character → false."a" is in A–Z / a–z."_" is treated as a word character."9" matches \w.Pull identifiers out of messy text with \w+.
const text = "hi_42! go-now";
console.log(text.match(/\w+/g));
// ["hi_42", "go", "now"]\w+. One or more word characters form a token.g flag finds every run.! and - break tokens apart.hi_42 is one token, not three.Allow only letters, digits, and underscore for the whole string.
console.log(/^\w+$/.test("user_1")); // true
console.log(/^\w+$/.test("user-1")); // false
console.log(/^\w+$/.test("")); // false^ and $ mean every character must match.\w+ rejects the empty string."user_1" passes."-" is not a word character → false.Check these before relying on \w in real projects.
\w is ASCII by defaultAccented letters like é and non-Latin scripts do not match. For Unicode letters, use property escapes with the u flag.
"user-name" fails /^\w+$/. Underscore is allowed; hyphen is not.
\w+ needs at least one character/^\w+$/.test("") is false. Use /^\w*$/ if the empty string should pass.
\w matches characters. For edges of words, use \b.
The \w word-character escape is core regex syntax (ES3+) and works everywhere JavaScript runs.
Supported in every modern and legacy browser, plus all Node.js versions. No polyfill required.
Bottom line: Safe to use in any JavaScript environment. Pair with \W when you need the non-word side.
| Approach | Cost | Best for |
|---|---|---|
/\w/.test(str) | O(n) | Quick “has word char?” checks |
str.match(/\w+/g) | O(n) | Tokenizing identifiers |
/^\w+$/.test(str) | O(n) | Username / ID validation |
Character-class style matches are cheap. Prefer \W when you want punctuation and spaces, and \w when you want the tokens.
\w matches one letter, digit, or underscore.\w+ to match identifiers and words./^\w+$/ requires the whole string to be word characters.\w.One line: \w means letter/digit/underscore — detect it, tokenize with \w+, or require a clean identifier with /^\w+$/.
Learn how two-digit hex escapes match byte values in patterns.
6 people found this page helpful