guardz/dist/typeguards/isNegativeNumber.d.ts

A simple and lightweight TypeScript type guard library for runtime type validation.

import type { NegativeNumber } from '../types/NegativeNumber';
import type { TypeGuardFn } from './isType';
/**
 * Checks if a value is a negative number (less than 0).
 *
 * Note: This excludes zero, positive numbers, NaN, and Infinity.
 *
 * @param value - The value to check
 * @param config - Optional configuration for error handling
 * @returns True if the value is a negative number, false otherwise
 *
 * @example
 * ```typescript
 * import { isNegativeNumber } from 'guardz';
 *
 * console.log(isNegativeNumber(-1)); // true
 * console.log(isNegativeNumber(-42.5)); // true
 * console.log(isNegativeNumber(-0.001)); // true
 * console.log(isNegativeNumber(0)); // false (zero is not negative)
 * console.log(isNegativeNumber(1)); // false
 * console.log(isNegativeNumber(0.1)); // false
 * console.log(isNegativeNumber(NaN)); // false
 * console.log(isNegativeNumber(-Infinity)); // false
 * console.log(isNegativeNumber("-5")); // false
 *
 * // With type narrowing
 * const data: unknown = getUserInput();
 * if (isNegativeNumber(data)) {
 *   // data is now typed as NegativeNumber
 *   console.log(Math.abs(data)); // Safe to convert to positive
 * }
 * ```
 */
export declare const isNegativeNumber: TypeGuardFn<NegativeNumber>;