is2DArray.ts

import { isArray, isEmpty } from "../base";

/**
 * Checks if the given input is a non-empty two-dimensional array, meaning it's an array where ***all*** its elements are also arrays.
 *
 * This function first ensures the input itself is an array. If not, it throws a `TypeError`.
 *
 * @param   {unknown} arr - The input to check.
 * @returns {boolean} `true` if the input is a non-empty array where all its elements are arrays; otherwise, `false`.
 * If `true`, TypeScript will **narrow the type of `arr`** to `Array<Array<unknown>>`,
 * allowing safer access to its elements as arrays.
 * @throws  {@link TypeError} If the input `arr` is not an array.
 * @since   1.0.0
 * @version 1.0.0
 */
export function is2DArray(arr: unknown): arr is Array<Array<unknown>> {
  if (!isArray(arr)) {
    throw new TypeError("Input must be an array.");
  }

  return !isEmpty(arr) && arr.every(isArray);
}