@akala/core/src/eachAsync.ts

# Context

import {isPromiseLike} from './helpers'

export type NextFunction = (error?, ...args: any[]) => void;

export function array<T>(array: T[] | ArrayLike<T>, body: (element: T, i: number, next: NextFunction) => void | PromiseLike<void>, complete: NextFunction)
{
    var loop = function (i)
    {
        if (i == array.length)
            complete();
        else
            try
            {
                var promise=body(array[i], i, function (error?)
                {
                    if (error)
                        complete(error);
                    else
                        setImmediate(loop, i + 1)
                });
                if(promise && isPromiseLike(promise))
                {
                    promise.then(()=>setImmediate(loop, i+1), complete);
                }
            }
            catch (e)
            {
                complete(e);
            }
    }
    loop(0);
}

export function object<T>(o: T, body: (element: T[keyof T], i: keyof T, next: NextFunction) => void, complete: NextFunction)
{
    array(Object.keys(o) as (keyof T)[], function (key, i, next)
    {
        body(o[key], key, next);
    }, complete);
}

export function each<T>(array: T[] | ArrayLike<T>, body: (element: T, i?: number, next?: NextFunction) => PromiseLike<void>, complete: NextFunction): void
export function each<T>(array: T[] | ArrayLike<T>, body: (element: T, i?: number, next?: NextFunction) => PromiseLike<void>): PromiseLike<void>
export function each<T>(array: T[] | ArrayLike<T>, body: (element: T, i: number, next: NextFunction) => void, complete: NextFunction): void
export function each(o: any, body: (element: any, i: string, next: NextFunction) => void, complete: NextFunction): void
export function each<T>(array: T[] | ArrayLike<T>, body: (element: T, i: number, next: NextFunction) => void): PromiseLike<void>
export function each(o: any, body: (element: any, i: string, next: NextFunction) => void): PromiseLike<void>
export function each(it: any, body: (element: any, i: any, next: NextFunction) => void, complete?: NextFunction): void | PromiseLike<void>
{
    if (complete)
    {
        if (Array.isArray(it) || typeof (it['length']) != 'undefined')
            return array(it, body, complete);
        return object(it, body, complete);

    }
    else
    {
        return new Promise((resolve, reject) =>
        {
            if (Array.isArray(it) || typeof (it['length']) != 'undefined')
                return array(it, body, function (err)
                {
                    if (err)
                        reject(err);
                    else
                        resolve();
                });
            return object(it, body, function (err)
            {
                if (err)
                    reject(err);
                else
                    resolve();
            });
        })
    }
}