normalizeNegativeNumber

Attempts to normalize a value into a negative number.

This helper never throws and never mutates input. Returns null if normalization fails.

Signature

function normalizeNegativeNumber(value: unknown): number | null

Parameters

Name	Type	Description
value	unknown	The value to normalize.

Returns

Returns a negative number, or null if normalization fails.

Examples

normalizeNegativeNumber(-0.1);       // → -0.1
normalizeNegativeNumber(-5);         // → -5
normalizeNegativeNumber("-3.14");    // → -3.14
normalizeNegativeNumber(" -42 ");    // → -42

normalizeNegativeNumber(0);          // → null
normalizeNegativeNumber(5);          // → null
normalizeNegativeNumber("0");        // → null
normalizeNegativeNumber("42");       // → null
normalizeNegativeNumber("abc");      // → null
normalizeNegativeNumber(NaN);        // → null
normalizeNegativeNumber(Infinity);   // → null
normalizeNegativeNumber(undefined);  // → null

Notes

• Only numbers less than zero (0) are accepted.
• Fractional numbers are allowed.
• Strings are trimmed and parsed; must represent a strictly negative number.
• Zero, positive numbers, NaN, Infinity, -Infinity, and non-numeric types return null.
• Use validateNegativeNumber for structured validation.