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JavaScript RegExp [0-9] Expression - GeeksforGeeks

JavaScript RegExp [0-9] Expression

Last Updated : 11 Jul, 2025

The [0-9] expression in JavaScript regular expressions matches any single digit between 0 and 9. It is a character class used to represent a range of numeric characters.

JavaScript


 let regex = /[0-9]/g;
let str = "abc123xyz";
let matches = str.match(regex);
console.log(matches);

The pattern [0-9] matches the digits 1, 2, and 3 in the string.

Syntax:

/[0-9]/

[0-9]: Matches a single numeric character (0 through 9).
Modifiers (optional): Can be used with flags like g, i, or m for global, case-insensitive, or multiline matching.

Key Points

Matches any digit from 0 to 9.
Equivalent to the shorthand \d in JavaScript regex.
Used in conjunction with quantifiers to match multiple digits or numeric patterns.
Works within larger patterns for specific use cases, such as parsing numbers from strings.

Real-World Examples 1. Finding Digits in a String JavaScript


 let regex = /[0-9]/g;
let str = "Contact: 555-123-4567";
let matches = str.match(regex);
console.log(matches);

Output

[
  '5', '5', '5', '1',
  '2', '3', '4', '5',
  '6', '7'
]

2. Extracting Numbers JavaScript


 let regex = /[0-9]+/g;
// Matches one or more digits
let str = "The order IDs are 123, 456, and 789.";
let matches = str.match(regex);
console.log(matches);

Output

[ '123', '456', '789' ]

The + quantifier ensures that consecutive digits are matched as a single number.

3. Validating Numeric Input JavaScript


 let regex = /^[0-9]+$/;
let input = "123456";
if (regex.test(input)) {
    console.log("Valid numeric input.");
} else {
    console.log("Invalid input.");
}

Output

Valid numeric input.

The pattern ^[0-9]+$ ensures the entire string consists only of digits.

4. Matching Numbers in a Date JavaScript


 let regex = /[0-9]{4}/;
// Matches exactly four digits
let str = "The year is 2024.";
let match = str.match(regex);
console.log(match);

Output

[ '2024', index: 12, input: 'The year is 2024.', groups: undefined ]

Here, [0-9]{4} matches a four-digit sequence representing a year.

5. Replacing Digits JavaScript


 let regex = /[0-9]/g;
let str = "Room 101";
let result = str.replace(regex, "*");
console.log(result);

This example replaces all digits in the string with asterisks (*).

Common Patterns Using [0-9]

Match a Single Digit:

/[0-9]/

Match Multiple Digits:

/[0-9]+/

Match a Fixed Number of Digits:

/[0-9]{3}/ // Matches exactly 3 digits

Match Digits at the Start of a String:

/^[0-9]+/

Match Digits Within Non-Digit Characters:

/\b[0-9]+\b/

Comparison: [0-9] vs \d

[0-9]: Matches only numeric characters (0 to 9).
\d: Matches numeric characters, but may match additional Unicode digits depending on the environment.

For strict numeric matching, [0-9] is often preferred.

Why Use [0-9]?

Precision: Clearly specifies a range of numeric characters.
Versatility: Works seamlessly with other regex patterns and modifiers.
Control: Provides explicit control over matching rules, avoiding ambiguity.

Conclusion

The [0-9] expression is a fundamental building block in JavaScript regex, perfect for handling numeric data in strings.

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