/**
 * Inserts an item into an array or updates an existing item. If a key is provided, it uses the key to find an existing item.
 * Otherwise, it uses a comparison function. the default comparison function is (a,b) => a === b，if all can't find an existing item, it simply adds the item to the end of the array.
 * @name arrayUpsert
 * @template T - The type of elements in the array.
 * @param {T[]} target - The array to upsert into.
 * @param {T} item - The item to insert or update in the array.
 * @param {keyof T} [compareKey] - The property name to identify the item. If provided, items are compared based on this property.
 * @param {(targetItem: T, item: T) => boolean} [compare] - A comparison function to determine if the item exists in the array. default compare (a,b) => a === b  (optional)
 * @param {boolean} [returnOriginal] - Flag to return the original array or a copy of the array after the upsert operation. Defaults to false.(optional)
 * @param merge - Flag to merge the item with the existing item. Defaults to false.(optional)
 * @returns {T[]} The array after the upsert operation.
 */
declare function arrayUpsert<T>(target: T[], item: T, compareKey?: keyof T, compare?: (targetItem: T, item: T) => boolean, returnOriginal?: boolean, merge?: boolean): T[];
export default arrayUpsert;