/** Storage item processor for parse/stringify value from storage automatically. */
export interface StorageValueProcessor<T> {
    /** Receives item from storage and should return what you want to receive from hook as value. */
    parse: (item: string | null) => T;
    /** Receives value and should return string for passing it as item to storage. */
    stringify: (item: T) => string;
}
/** Options of `useStorageItem` hook.  */
export interface UseStorageItemOptions<T> {
    /** Storage. Usually localStorage or sessionStorage. */
    storage: Storage | (() => Storage);
    /** Item value processor. */
    processor: StorageValueProcessor<T>;
    /** Default value. */
    defaultValue?: string | null;
}
/** Return value type of `useStorageItem` hook. */
export type UseStorageItemReturn<T> = [T, (value: T | null) => void];
/**
 * Hook for working with storage item.
 * You need to provide key and storage for getting actual value from storage.
 *
 * By default result value is raw value from storage.
 * You can provide processor for parse/stringify value automatically.
 *
 * @param key Storage item key.
 * @param options Options.
 * @returns Tuple like `[state, setState]`.
 */
export declare function useStorageItem(key: string, options: {
    storage: Storage | (() => Storage);
    processor?: StorageValueProcessor<string | null>;
    defaultValue?: string | null;
}): UseStorageItemReturn<string | null>;
/**
 * Hook for working with storage item.
 *
 * You need to provide key and storage for getting actual value from storage.
 *
 * By default result value is raw value from storage.
 *
 * You can provide processor for parse/stringify value automatically.
 *
 * @param key Storage item key.
 * @param options Options.
 * @returns Tuple like `[state, setState]`.
 */
export declare function useStorageItem<T>(key: string, options: UseStorageItemOptions<T>): UseStorageItemReturn<T>;
/**
 * Returns JSON value processor for using in `useStorageItem` options.
 * @param placeholder Placeholder. Will be used when storage item is empty or when JSON.parse is failed.
 * @returns Processor.
 */
export declare function getJsonProcessor<T>(placeholder: T): StorageValueProcessor<T>;