export type Results<T = any> = T[] & {
    first: T;
    _firstFlag: boolean;
};
export type SimpleCallback = () => any;
export interface AsyncParallelIteratorCallback<T = unknown, E = unknown> {
    (err?: E | null, value?: T): void;
}
export interface AsyncParallelIterator<T, E> {
    (item: T, callback: AsyncParallelIteratorCallback<T, E>): void;
}
export interface AsyncIterator<T, E> {
    (item: T, callback: ErrorCallback<E>): void;
}
export interface ErrorCallback<T> {
    (err?: T | null): void;
}
export type AsyncParallelCallback<T, E> = (finishedNum: number, values: Results<T>, errors: Results<E>, done: SimpleCallback) => any;
export declare function each<T = unknown, E = unknown>(targets: T[], handler: AsyncIterator<T, E>, cb?: ErrorCallback<E>): void;