/**
 * Flattens an array to a specified depth, converting nested arrays into a single-level array.
 *
 * @template T - The type of elements in the array
 * @param array - The array to flatten
 * @param depth - The depth level specifying how deep a nested array structure should be flattened (default: 1)
 * @returns A new flattened array
 *
 * @example
 * // Flatten one level deep (default)
 * const nested = [1, [2, 3], [4, [5, 6]]];
 * const result = flatten(nested);
 * console.log(result); // [1, 2, 3, 4, [5, 6]]
 *
 * @example
 * // Flatten completely (infinite depth)
 * const deepNested = [1, [2, [3, [4, 5]]]];
 * const result = flatten(deepNested, Infinity);
 * console.log(result); // [1, 2, 3, 4, 5]
 *
 * @example
 * // Flatten to specific depth
 * const mixed = [1, [2, [3, [4, 5]]]];
 * const result = flatten(mixed, 2);
 * console.log(result); // [1, 2, 3, [4, 5]]
 *
 * @example
 * // With objects and mixed types
 * const data = [
 *   { id: 1 },
 *   [{ id: 2 }, { id: 3 }],
 *   [{ id: 4 }, [{ id: 5 }]]
 * ];
 * const result = flatten(data);
 * console.log(result); // [{ id: 1 }, { id: 2 }, { id: 3 }, { id: 4 }, [{ id: 5 }]]
 */
export declare function flatten<T>(array: readonly (T | readonly any[])[], depth?: number): T[];