\d?\d matches any single ASCII digit from 0 through 9. It is shorthand for [0-9]. The inverse is \D (any non-digit).
\d → one digit 0–9 (same as [0-9])
\d+ → one or more digits
\d{4} → exactly four digits
\D → one non-digit (same as [^0-9])
/\d/.test("room 5") → true
/\d/.test("hello") → false
"a12b".match(/\d+/g) → ["12"]| Use | Prefer |
|---|---|
| Detect a digit | /\d/ |
| Extract numbers | /\d+/g |
| Fixed-length code | /^\d{4}$/ |
| Non-digit character | /\D/ |
\dMatch one digit, then add a quantifier when you need a full number or fixed length.
/\d/ to test for any digit in a string.\d+ (or \d{n}) when you need more than one digit.^ and $ when the whole string must be digits only.\D when you want the opposite: anything that is not a digit.| Piece | Required? | Role |
|---|---|---|
\d in the pattern | Yes | Match one digit 0–9 |
Quantifier (+, {n}) | Optional | Match runs or fixed counts |
g flag | Optional | Find every digit / number run |
Anchors ^ $ | For full-string checks | Validate the entire value |
pattern has "\d"
read next character ch from the string
if ch is '0'..'9':
accept match
else:
fail this path
common patterns:
/\d/ → any digit present?
/\d+/g → every number token
/^\d{4}$/ → exactly four digits
/\D/ → any non-digitKeep these facts handy when matching digits.
| Topic | Detail |
|---|---|
| Matches | One ASCII digit 0–9 |
| Equivalent | [0-9] |
| Inverse | \D / [^0-9] |
| One or more | \d+ |
| Exact count | \d{4}, \d{2,4} |
| Unicode digits | Not matched by default \d |
| Standard | ES3+ (universal) |
Run common \d operations on sample text.
Short, copy-ready snippets. Open DevTools Console, or use Try It Yourself for a live editor.
Return true when the text contains at least one digit.
console.log(/\d/.test("hello")); // false
console.log(/\d/.test("room 5")); // true
console.log(/\d/.test("Order #42")); // true"hello" has no 0–9 → false."room 5" contains 5 → true."Order #42" matches on 4 (or 2).\d does not require the whole string to be numeric.Collect every run of consecutive digits with \d+ and the g flag.
const text = "SKU-12 costs $19.99 today";
const numbers = text.match(/\d+/g);
console.log(numbers); // ["12", "19", "99"]
const first = text.match(/\d+/);
console.log(first[0]); // "12"+ means one or more. Digits stick together into tokens like "12".g returns all matches, not only the first.19.99 becomes "19" and "99" because . is not a digit.g, match(/\d+/) gives the first number token.Require the entire string to be exactly four digits.
const pinPattern = /^\d{4}$/;
console.log(pinPattern.test("4821")); // true
console.log(pinPattern.test("482")); // false
console.log(pinPattern.test("4821a")); // false
console.log(pinPattern.test("48 21")); // false^ and $. The match must cover the whole string.\d{4}. Exactly four digit characters in a row."48 21" is not four digits — the space breaks the pattern.Check these before relying on \d in real projects.
"19.99".match(/\d+/g) is ["19", "99"]. For simple floats use a pattern that includes \..
Default \d does not match Unicode numerals. For most forms and IDs, ASCII 0–9 is what you want.
new RegExp needs double escapingWrite new RegExp("\\d+"). In a string pattern argument you need two backslashes.
The \d digit metacharacter is core regex syntax (ES3+) and works everywhere JavaScript runs.
Supported in every modern and legacy browser, plus all Node.js versions. \d and [0-9] behave identically for ASCII digits.
Bottom line: Safe everywhere. Use \d as the standard shorthand for matching digits 0–9.
| Approach | Cost | Best for |
|---|---|---|
/\d/.test(str) | O(n) | Quick digit presence checks |
str.match(/\d+/g) | O(n) | Extract all number tokens |
/^\d{n}$/.test(str) | O(n) | Fixed-length validation |
Matching digits is cheap. Prefer a clear pattern (\d+, ^\d{4}$) over complicated classes — engines optimize the digit shorthand well.
\d matches one ASCII digit 0–9 (same as [0-9]).\d+ or \d{n} for longer numbers and codes.\D matches any non-digit.^…$ when the whole string must be digits.One line: \d finds digits — use \d+ to extract numbers and /^\d{n}$/ to validate fixed-length codes.
Learn how the dot metacharacter matches almost any character.
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