Integer Validation Regex (Positive or Negative)

Validate integers that can be positive, negative, or zero using a simple regex pattern with optional minus sign.

Pattern Breakdown

^-?\d+$

Components

Character Classes

• -? - Optional minus sign (zero or one occurrence)
• \d - Any digit (0-9)
• + - Quantifier: one or more occurrences

Examples

Valid:

• 0
• 123
• -123
• 999999
• -1000000

Invalid:

• 12.5 (decimal)
• +5 (plus sign)
• 123 (leading space)
• 123 (trailing space)
• - (just minus sign)
• abc (non-numeric)

Implementation

JavaScript

const integerRegex = /^-?\d+$/;
integerRegex.test('123'); // true
integerRegex.test('-123'); // true
integerRegex.test('0'); // true
integerRegex.test('12.5'); // false (decimal)
integerRegex.test('+5'); // false (plus sign)

Python

import re
integer_regex = r'^-?\d+$'
bool(re.match(integer_regex, '123'))  # True
bool(re.match(integer_regex, '-123'))  # True
bool(re.match(integer_regex, '0'))  # True
bool(re.match(integer_regex, '12.5'))  # False (decimal)

Go

integerRegex := regexp.MustCompile(`^-?\d+$`)
integerRegex.MatchString("123") // true
integerRegex.MatchString("-123") // true
integerRegex.MatchString("0") // true
integerRegex.MatchString("12.5") // false (decimal)

Limitations

1. Includes zero: Matches 0 (and -0)
2. No leading zeros: Accepts 0123 (may want to prevent this)
3. No size limit: Doesn't enforce maximum/minimum value
4. String validation: Validates string format, not actual integer type
5. No scientific notation: Doesn't support 1e5 format

When to Use

• Integer input validation (any sign)
• General number input forms
• When you need flexible integer validation
• Form input validation
• Quick integer format checking

For production, consider:

• Preventing leading zeros: ^-?(0|[1-9]\d*)$
• Adding value range validation
• Converting to integer type after validation
• Handling edge cases for very large numbers
• Supporting plus sign if needed: ^[+-]?\d+$