import type { _Storage } from './types';
/**
 * Allows the addition, modification, or deletion of stored data items.
 */
export declare class Storage implements _Storage {
    private storage;
    /**
     * Returns an integer representing the number of data items stored in the
     * `Storage` object.
     */
    get length(): number;
    /**
     * When invoked, will empty all keys out of the storage.
     */
    clear(): void;
    /**
     * When passed a key name, will return that key's value.
     * @returns the value of the key or `null` if the key does not exist.
     */
    getItem(keyName: string): string | null;
    /**
     * When passed a number `index`, this method will return the name of the
     * nth key in the storage.
     * @returns the value of the key or `null` if the key does not exist.
     */
    key(
    /**
     * The number of the key for which you want the name. This is
     * a zero-based value.
     */
    index: number): string;
    /**
     * When passed a key name, will remove that key from the storage.
     */
    removeItem(keyName: string): void;
    /**
     * When passed a key name and value, will add that key to the storage,
     * or update that key's value if it already exists.
     * @throws if the storage is full. Particularly, in Mobile Safari
     * (Safari sets the quota to `0` bytes in private mode, unlike other browsers,
     * which allow storage in private mode using separate data containers.)
     * Hence developers should make sure to **always** catch possible exceptions
     * from `setItem()`**.
     */
    setItem(keyName: string, 
    /**
     * The value is converted into a string.
     */
    value: string): void;
}