JavaScript RegExp [0-9] Character Class

What Is [0-9]?

[0-9] is a character class that matches one ASCII digit from 0 through 9. In JavaScript it matches the same digits as \d.

/[0-9]/     → one digit (0…9)
/[0-9]+/    → one or more digits
/[0-9]{4}/  → exactly four digits

same idea as /\d/ in JavaScript
[^0-9]      → one non-digit

How to Use [0-9]

Put the class in a pattern, add a quantifier if needed, then test or extract.

1. Write [0-9] inside your regex for one digit.
2. Add +, *, or {n} when you need more than one digit.
3. Use test() for yes/no, or exec() / match() to read the digits.
4. Prefer ^…$ when the whole string must be digits only (e.g. a PIN).

Pseudocode

pattern = /[0-9]/          // or /[0-9]+/, /[0-9]{n}/
str = text to check

if pattern.test(str):
    // at least one digit found (for /[0-9]/)

match = pattern.exec(str)
// match[0] is the digit (or digit run)

Cheat Sheet

Keep these patterns handy while matching digits.

Live Preview

Pick a sample string and see whether /[0-9]/ finds a digit.

str = "Room 7"
/[0-9]/.test(str) → true
exec → "7" (index 5)

JavaScript Examples

Short, copy-ready snippets. Open DevTools Console, or use Try It Yourself for a live editor.

const digit = /[0-9]/;

console.log(digit.test("Room 7"));  // true
console.log(digit.test("Hello"));   // false
console.log(digit.exec("A4B")[0]);  // "4"

true
false
4

const numbers = /[0-9]+/g;
const str = "Order 12 and 345";

console.log(str.match(numbers));
// ["12", "345"]

12,345

const pin = /^[0-9]{4}$/;

console.log(pin.test("9081"));  // true
console.log(pin.test("42"));    // false
console.log(pin.test("90a1"));  // false

true
false
false

Performance Notes

Digit classes are cheap. Prefer a clear pattern ([0-9] or \d) over hand-rolled loops when validating or extracting numbers.

Key Takeaways