/**
 * Immutably adds the item to the array if it's not already included; removes it if it's already included
 *
 * @since v0.0.1
 * @category Array
 * @template {T} - The type of the array
 * @param {T[]} array - The original array
 * @param {T} item - The item to toggle
 * @param {(item: T) => R} [reducer] - Optional function to take an array item and reduce it to a value that will be used as the basis for the toggle comparison
 * @returns {T[]}
 * @example
 * const array = [1, 2, 3];
 *
 * toggle(array, 4)   //=> [1, 2, 3, 4]
 * toggle(array, 2)   //=> [1, 3]
 * @example
 * const array = [{ id: 1, value: 'a' }, { id: 2, value: 'b' }];
 * const reducer = x => x.id;
 *
 * toggle(array, { id: 3, value: 'c' }, reducer);
 * //=> [{ id: 1, value: 'a' }, { id: 2, value: 'b' }, { id: 3, value: 'c' }]
 *
 * toggle(array, { id: 1, value: 'a' }, reducer);
 * //=> [{ id: 2, value: 'b' }]
 */
export declare const toggle: <T = unknown, R = unknown>(array: T[], item: T, reducer?: (item: T) => R) => T[];