/**
 * Creates an object composed of keys generated from the results of running each element
 * of collection through iteratee. The corresponding value of each key is an array of
 * elements responsible for generating the key.
 *
 * @param array - The collection to iterate over
 * @param iteratee - The function invoked per iteration or property name to group by
 * @returns The composed aggregate object
 *
 * @example
 * ```ts
 * groupBy([6.1, 4.2, 6.3], Math.floor);
 * // => { '4': [4.2], '6': [6.1, 6.3] }
 *
 * groupBy(['one', 'two', 'three'], 'length');
 * // => { '3': ['one', 'two'], '5': ['three'] }
 * ```
 */
export declare function groupBy<T>(array: T[], iteratee: ((value: T) => string | number) | keyof T): Record<string, T[]>;