guardz/dist/typeguards/isIndexSignature.d.ts

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

import type { TypeGuardFn } from './isType';
/**
 * Creates a type guard that validates objects with index signatures.
 *
 * This function validates that an object has properties with keys of a specific type
 * and values of a specific type. It's useful for validating objects with dynamic keys
 * like `{ [key: string]: T }` or `{ [key: number]: T }`.
 *
 * Note: For number keys, this validates that the string keys can be converted to numbers.
 * JavaScript object keys are always strings, so `{ 1: true }` becomes `{ "1": true }`.
 *
 * @template K - The type of the keys (string or number)
 * @template V - The type of the values
 * @param keyGuard - Type guard function for validating keys
 * @param valueGuard - Type guard function for validating values
 * @returns A type guard function that validates index signature objects
 *
 * @example
 * ```typescript
 * import { isIndexSignature, isString, isNumber, isBoolean } from 'guardz';
 *
 * // String-keyed object with number values
 * const isStringNumberMap = isIndexSignature(isString, isNumber);
 *
 * // Number-keyed object with boolean values
 * const isNumberBooleanMap = isIndexSignature(isNumber, isBoolean);
 *
 * console.log(isStringNumberMap({ a: 1, b: 2, c: 3 })); // true
 * console.log(isStringNumberMap({ "key1": 10, "key2": 20 })); // true
 * console.log(isStringNumberMap({ a: 1, b: "2" })); // false (mixed value types)
 * console.log(isStringNumberMap({ 1: "a", 2: "b" })); // false (number keys)
 *
 * console.log(isNumberBooleanMap({ 1: true, 2: false })); // true
 * console.log(isNumberBooleanMap({ "1": true })); // true (string keys that are numbers)
 * console.log(isNumberBooleanMap({ "abc": true })); // false (non-numeric string keys)
 *
 * // With type narrowing
 * const data: unknown = getDataFromAPI();
 * if (isStringNumberMap(data)) {
 *   // data is now typed as { [key: string]: number }
 *   Object.entries(data).forEach(([key, value]) => {
 *     console.log(`${key}: ${value * 2}`); // Safe to use as number
 *   });
 * }
 * ```
 */
export declare function isIndexSignature<K extends string | number, V>(keyGuard: TypeGuardFn<K>, valueGuard: TypeGuardFn<V>): TypeGuardFn<{
    [P in K]: V;
}>;