async.mjs

 * @param {Function} [callback] - A callback which is called after all the
 * `iteratee` functions have finished. Invoked with (err, results).
 * @returns {Promise} a promise, if no callback provided
 * @example
 *
 * // dir1 is a directory that contains file1.txt, file2.txt
 * // dir2 is a directory that contains file3.txt, file4.txt
 * // dir3 is a directory that contains file5.txt
 *
 * const files = ['dir1/file1.txt','dir2/file3.txt','dir3/file6.txt'];
 *
 * // asynchronous function that checks if a file exists
 * function fileExists(file, callback) {
 *    fs.access(file, fs.constants.F_OK, (err) => {
 *        callback(null, !err);
 *    });
 * }
 *
 * // Using callbacks
 * async.filter(files, fileExists, function(err, results) {
 *    if(err) {
 *        console.log(err);
 *    } else {
 *        console.log(results);
 *        // [ 'dir1/file1.txt', 'dir2/file3.txt' ]
 *        // results is now an array of the existing files
 *    }
 * });
 *
 * // Using Promises
 * async.filter(files, fileExists)
 * .then(results => {
 *     console.log(results);
 *     // [ 'dir1/file1.txt', 'dir2/file3.txt' ]
 *     // results is now an array of the existing files
 * }).catch(err => {
 *     console.log(err);
 * });
 *
 * // Using async/await
 * async () => {
 *     try {
 *         let results = await async.filter(files, fileExists);
 *         console.log(results);
 *         // [ 'dir1/file1.txt', 'dir2/file3.txt' ]
 *         // results is now an array of the existing files
 *     }
 *     catch (err) {
 *         console.log(err);
 *     }
 * }
 *
 */
function filter (coll, iteratee, callback) {
    return _filter(eachOf$1, coll, iteratee, callback)
}
var filter$1 = awaitify(filter, 3);

/**
 * The same as [`filter`]{@link module:Collections.filter} but runs a maximum of `limit` async operations at a
 * time.
 *
 * @name filterLimit
 * @static
 * @memberOf module:Collections
 * @method
 * @see [async.filter]{@link module:Collections.filter}
 * @alias selectLimit
 * @category Collection
 * @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
 * @param {number} limit - The maximum number of async operations at a time.
 * @param {Function} iteratee - A truth test to apply to each item in `coll`.
 * The `iteratee` is passed a `callback(err, truthValue)`, which must be called
 * with a boolean argument once it has completed. Invoked with (item, callback).
 * @param {Function} [callback] - A callback which is called after all the
 * `iteratee` functions have finished. Invoked with (err, results).
 * @returns {Promise} a promise, if no callback provided
 */
function filterLimit (coll, limit, iteratee, callback) {
    return _filter(eachOfLimit(limit), coll, iteratee, callback)
}
var filterLimit$1 = awaitify(filterLimit, 4);

/**
 * The same as [`filter`]{@link module:Collections.filter} but runs only a single async operation at a time.
 *
 * @name filterSeries
 * @static
 * @memberOf module:Collections
 * @method
 * @see [async.filter]{@link module:Collections.filter}
 * @alias selectSeries
 * @category Collection
 * @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
 * @param {Function} iteratee - A truth test to apply to each item in `coll`.
 * The `iteratee` is passed a `callback(err, truthValue)`, which must be called
 * with a boolean argument once it has completed. Invoked with (item, callback).
 * @param {Function} [callback] - A callback which is called after all the
 * `iteratee` functions have finished. Invoked with (err, results)
 * @returns {Promise} a promise, if no callback provided
 */
function filterSeries (coll, iteratee, callback) {
    return _filter(eachOfSeries$1, coll, iteratee, callback)
}
var filterSeries$1 = awaitify(filterSeries, 3);

/**
 * Calls the asynchronous function `fn` with a callback parameter that allows it
 * to call itself again, in series, indefinitely.

 * If an error is passed to the callback then `errback` is called with the
 * error, and execution stops, otherwise it will never be called.
 *
 * @name forever
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @category Control Flow
 * @param {AsyncFunction} fn - an async function to call repeatedly.
 * Invoked with (next).
 * @param {Function} [errback] - when `fn` passes an error to it's callback,
 * this function will be called, and execution stops. Invoked with (err).
 * @returns {Promise} a promise that rejects if an error occurs and an errback
 * is not passed
 * @example
 *
 * async.forever(
 *     function(next) {
 *         // next is suitable for passing to things that need a callback(err [, whatever]);
 *         // it will result in this function being called again.
 *     },
 *     function(err) {
 *         // if next is called with a value in its first parameter, it will appear
 *         // in here as 'err', and execution will stop.
 *     }
 * );
 */
function forever(fn, errback) {
    var done = onlyOnce(errback);
    var task = wrapAsync(ensureAsync(fn));

    function next(err) {
        if (err) return done(err);
        if (err === false) return;
        task(next);
    }
    return next();
}
var forever$1 = awaitify(forever, 2);

/**
 * The same as [`groupBy`]{@link module:Collections.groupBy} but runs a maximum of `limit` async operations at a time.
 *
 * @name groupByLimit
 * @static
 * @memberOf module:Collections
 * @method
 * @see [async.groupBy]{@link module:Collections.groupBy}
 * @category Collection
 * @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
 * @param {number} limit - The maximum number of async operations at a time.
 * @param {AsyncFunction} iteratee - An async function to apply to each item in
 * `coll`.
 * The iteratee should complete with a `key` to group the value under.
 * Invoked with (value, callback).
 * @param {Function} [callback] - A callback which is called when all `iteratee`
 * functions have finished, or an error occurs. Result is an `Object` whoses
 * properties are arrays of values which returned the corresponding key.
 * @returns {Promise} a promise, if no callback is passed
 */
function groupByLimit(coll, limit, iteratee, callback) {
    var _iteratee = wrapAsync(iteratee);
    return mapLimit$1(coll, limit, (val, iterCb) => {
        _iteratee(val, (err, key) => {
            if (err) return iterCb(err);
            return iterCb(err, {key, val});
        });
    }, (err, mapResults) => {
        var result = {};
        // from MDN, handle object having an `hasOwnProperty` prop
        var {hasOwnProperty} = Object.prototype;

        for (var i = 0; i < mapResults.length; i++) {
            if (mapResults[i]) {
                var {key} = mapResults[i];
                var {val} = mapResults[i];

                if (hasOwnProperty.call(result, key)) {
                    result[key].push(val);
                } else {
                    result[key] = [val];
                }
            }
        }

        return callback(err, result);
    });
}

var groupByLimit$1 = awaitify(groupByLimit, 4);

/**
 * Returns a new object, where each value corresponds to an array of items, from
 * `coll`, that returned the corresponding key. That is, the keys of the object
 * correspond to the values passed to the `iteratee` callback.
 *
 * Note: Since this function applies the `iteratee` to each item in parallel,
 * there is no guarantee that the `iteratee` functions will complete in order.
 * However, the values for each key in the `result` will be in the same order as
 * the original `coll`. For Objects, the values will roughly be in the order of
 * the original Objects' keys (but this can vary across JavaScript engines).
 *
 * @name groupBy
 * @static
 * @memberOf module:Collections
 * @method
 * @category Collection
 * @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
 * @param {AsyncFunction} iteratee - An async function to apply to each item in
 * `coll`.
 * The iteratee should complete with a `key` to group the value under.
 * Invoked with (value, callback).
 * @param {Function} [callback] - A callback which is called when all `iteratee`
 * functions have finished, or an error occurs. Result is an `Object` whoses
 * properties are arrays of values which returned the corresponding key.
 * @returns {Promise} a promise, if no callback is passed
 * @example
 *
 * // dir1 is a directory that contains file1.txt, file2.txt
 * // dir2 is a directory that contains file3.txt, file4.txt
 * // dir3 is a directory that contains file5.txt
 * // dir4 does not exist
 *
 * const files = ['dir1/file1.txt','dir2','dir4']
 *
 * // asynchronous function that detects file type as none, file, or directory
 * function detectFile(file, callback) {
 *     fs.stat(file, function(err, stat) {
 *         if (err) {
 *             return callback(null, 'none');
 *         }
 *         callback(null, stat.isDirectory() ? 'directory' : 'file');
 *     });
 * }
 *
 * //Using callbacks
 * async.groupBy(files, detectFile, function(err, result) {
 *     if(err) {
 *         console.log(err);
 *     } else {
 *	       console.log(result);
 *         // {
 *         //     file: [ 'dir1/file1.txt' ],
 *         //     none: [ 'dir4' ],
 *         //     directory: [ 'dir2']
 *         // }
 *         // result is object containing the files grouped by type
 *     }
 * });
 *
 * // Using Promises
 * async.groupBy(files, detectFile)
 * .then( result => {
 *     console.log(result);
 *     // {
 *     //     file: [ 'dir1/file1.txt' ],
 *     //     none: [ 'dir4' ],
 *     //     directory: [ 'dir2']
 *     // }
 *     // result is object containing the files grouped by type
 * }).catch( err => {
 *     console.log(err);
 * });
 *
 * // Using async/await
 * async () => {
 *     try {
 *         let result = await async.groupBy(files, detectFile);
 *         console.log(result);
 *         // {
 *         //     file: [ 'dir1/file1.txt' ],
 *         //     none: [ 'dir4' ],
 *         //     directory: [ 'dir2']
 *         // }
 *         // result is object containing the files grouped by type
 *     }
 *     catch (err) {
 *         console.log(err);
 *     }
 * }
 *
 */
function groupBy (coll, iteratee, callback) {
    return groupByLimit$1(coll, Infinity, iteratee, callback)
}

/**
 * The same as [`groupBy`]{@link module:Collections.groupBy} but runs only a single async operation at a time.
 *
 * @name groupBySeries
 * @static
 * @memberOf module:Collections
 * @method
 * @see [async.groupBy]{@link module:Collections.groupBy}
 * @category Collection
 * @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
 * @param {AsyncFunction} iteratee - An async function to apply to each item in
 * `coll`.
 * The iteratee should complete with a `key` to group the value under.
 * Invoked with (value, callback).
 * @param {Function} [callback] - A callback which is called when all `iteratee`
 * functions have finished, or an error occurs. Result is an `Object` whose
 * properties are arrays of values which returned the corresponding key.
 * @returns {Promise} a promise, if no callback is passed
 */
function groupBySeries (coll, iteratee, callback) {
    return groupByLimit$1(coll, 1, iteratee, callback)
}

/**
 * Logs the result of an `async` function to the `console`. Only works in
 * Node.js or in browsers that support `console.log` and `console.error` (such
 * as FF and Chrome). If multiple arguments are returned from the async
 * function, `console.log` is called on each argument in order.
 *
 * @name log
 * @static
 * @memberOf module:Utils
 * @method
 * @category Util
 * @param {AsyncFunction} function - The function you want to eventually apply
 * all arguments to.
 * @param {...*} arguments... - Any number of arguments to apply to the function.
 * @example
 *
 * // in a module
 * var hello = function(name, callback) {
 *     setTimeout(function() {
 *         callback(null, 'hello ' + name);
 *     }, 1000);
 * };
 *
 * // in the node repl
 * node> async.log(hello, 'world');
 * 'hello world'
 */
var log = consoleFunc('log');

/**
 * The same as [`mapValues`]{@link module:Collections.mapValues} but runs a maximum of `limit` async operations at a
 * time.
 *
 * @name mapValuesLimit
 * @static
 * @memberOf module:Collections
 * @method
 * @see [async.mapValues]{@link module:Collections.mapValues}
 * @category Collection
 * @param {Object} obj - A collection to iterate over.
 * @param {number} limit - The maximum number of async operations at a time.
 * @param {AsyncFunction} iteratee - A function to apply to each value and key
 * in `coll`.
 * The iteratee should complete with the transformed value as its result.
 * Invoked with (value, key, callback).
 * @param {Function} [callback] - A callback which is called when all `iteratee`
 * functions have finished, or an error occurs. `result` is a new object consisting
 * of each key from `obj`, with each transformed value on the right-hand side.
 * Invoked with (err, result).
 * @returns {Promise} a promise, if no callback is passed
 */
function mapValuesLimit(obj, limit, iteratee, callback) {
    callback = once(callback);
    var newObj = {};
    var _iteratee = wrapAsync(iteratee);
    return eachOfLimit(limit)(obj, (val, key, next) => {
        _iteratee(val, key, (err, result) => {
            if (err) return next(err);
            newObj[key] = result;
            next(err);
        });
    }, err => callback(err, newObj));
}

var mapValuesLimit$1 = awaitify(mapValuesLimit, 4);

/**
 * A relative of [`map`]{@link module:Collections.map}, designed for use with objects.
 *
 * Produces a new Object by mapping each value of `obj` through the `iteratee`
 * function. The `iteratee` is called each `value` and `key` from `obj` and a
 * callback for when it has finished processing. Each of these callbacks takes
 * two arguments: an `error`, and the transformed item from `obj`. If `iteratee`
 * passes an error to its callback, the main `callback` (for the `mapValues`
 * function) is immediately called with the error.
 *
 * Note, the order of the keys in the result is not guaranteed.  The keys will
 * be roughly in the order they complete, (but this is very engine-specific)
 *
 * @name mapValues
 * @static
 * @memberOf module:Collections
 * @method
 * @category Collection
 * @param {Object} obj - A collection to iterate over.
 * @param {AsyncFunction} iteratee - A function to apply to each value and key
 * in `coll`.
 * The iteratee should complete with the transformed value as its result.
 * Invoked with (value, key, callback).
 * @param {Function} [callback] - A callback which is called when all `iteratee`
 * functions have finished, or an error occurs. `result` is a new object consisting
 * of each key from `obj`, with each transformed value on the right-hand side.
 * Invoked with (err, result).
 * @returns {Promise} a promise, if no callback is passed
 * @example
 *
 * // file1.txt is a file that is 1000 bytes in size
 * // file2.txt is a file that is 2000 bytes in size
 * // file3.txt is a file that is 3000 bytes in size
 * // file4.txt does not exist
 *
 * const fileMap = {
 *     f1: 'file1.txt',
 *     f2: 'file2.txt',
 *     f3: 'file3.txt'
 * };
 *
 * const withMissingFileMap = {
 *     f1: 'file1.txt',
 *     f2: 'file2.txt',
 *     f3: 'file4.txt'
 * };
 *
 * // asynchronous function that returns the file size in bytes
 * function getFileSizeInBytes(file, key, callback) {
 *     fs.stat(file, function(err, stat) {
 *         if (err) {
 *             return callback(err);
 *         }
 *         callback(null, stat.size);
 *     });
 * }
 *
 * // Using callbacks
 * async.mapValues(fileMap, getFileSizeInBytes, function(err, result) {
 *     if (err) {
 *         console.log(err);
 *     } else {
 *         console.log(result);
 *         // result is now a map of file size in bytes for each file, e.g.
 *         // {
 *         //     f1: 1000,
 *         //     f2: 2000,
 *         //     f3: 3000
 *         // }
 *     }
 * });
 *
 * // Error handling
 * async.mapValues(withMissingFileMap, getFileSizeInBytes, function(err, result) {
 *     if (err) {
 *         console.log(err);
 *         // [ Error: ENOENT: no such file or directory ]
 *     } else {
 *         console.log(result);
 *     }
 * });
 *
 * // Using Promises
 * async.mapValues(fileMap, getFileSizeInBytes)
 * .then( result => {
 *     console.log(result);
 *     // result is now a map of file size in bytes for each file, e.g.
 *     // {
 *     //     f1: 1000,
 *     //     f2: 2000,
 *     //     f3: 3000
 *     // }
 * }).catch (err => {
 *     console.log(err);
 * });
 *
 * // Error Handling
 * async.mapValues(withMissingFileMap, getFileSizeInBytes)
 * .then( result => {
 *     console.log(result);
 * }).catch (err => {
 *     console.log(err);
 *     // [ Error: ENOENT: no such file or directory ]
 * });
 *
 * // Using async/await
 * async () => {
 *     try {
 *         let result = await async.mapValues(fileMap, getFileSizeInBytes);
 *         console.log(result);
 *         // result is now a map of file size in bytes for each file, e.g.
 *         // {
 *         //     f1: 1000,
 *         //     f2: 2000,
 *         //     f3: 3000
 *         // }
 *     }
 *     catch (err) {
 *         console.log(err);
 *     }
 * }
 *
 * // Error Handling
 * async () => {
 *     try {
 *         let result = await async.mapValues(withMissingFileMap, getFileSizeInBytes);
 *         console.log(result);
 *     }
 *     catch (err) {
 *         console.log(err);
 *         // [ Error: ENOENT: no such file or directory ]
 *     }
 * }
 *
 */
function mapValues(obj, iteratee, callback) {
    return mapValuesLimit$1(obj, Infinity, iteratee, callback)
}

/**
 * The same as [`mapValues`]{@link module:Collections.mapValues} but runs only a single async operation at a time.
 *
 * @name mapValuesSeries
 * @static
 * @memberOf module:Collections
 * @method
 * @see [async.mapValues]{@link module:Collections.mapValues}
 * @category Collection
 * @param {Object} obj - A collection to iterate over.
 * @param {AsyncFunction} iteratee - A function to apply to each value and key
 * in `coll`.
 * The iteratee should complete with the transformed value as its result.
 * Invoked with (value, key, callback).
 * @param {Function} [callback] - A callback which is called when all `iteratee`
 * functions have finished, or an error occurs. `result` is a new object consisting
 * of each key from `obj`, with each transformed value on the right-hand side.
 * Invoked with (err, result).
 * @returns {Promise} a promise, if no callback is passed
 */
function mapValuesSeries(obj, iteratee, callback) {
    return mapValuesLimit$1(obj, 1, iteratee, callback)
}

/**
 * Caches the results of an async function. When creating a hash to store
 * function results against, the callback is omitted from the hash and an
 * optional hash function can be used.
 *
 * **Note: if the async function errs, the result will not be cached and
 * subsequent calls will call the wrapped function.**
 *
 * If no hash function is specified, the first argument is used as a hash key,
 * which may work reasonably if it is a string or a data type that converts to a
 * distinct string. Note that objects and arrays will not behave reasonably.
 * Neither will cases where the other arguments are significant. In such cases,
 * specify your own hash function.
 *
 * The cache of results is exposed as the `memo` property of the function
 * returned by `memoize`.
 *
 * @name memoize
 * @static
 * @memberOf module:Utils
 * @method
 * @category Util
 * @param {AsyncFunction} fn - The async function to proxy and cache results from.
 * @param {Function} hasher - An optional function for generating a custom hash
 * for storing results. It has all the arguments applied to it apart from the
 * callback, and must be synchronous.
 * @returns {AsyncFunction} a memoized version of `fn`
 * @example
 *
 * var slow_fn = function(name, callback) {
 *     // do something
 *     callback(null, result);
 * };
 * var fn = async.memoize(slow_fn);
 *
 * // fn can now be used as if it were slow_fn
 * fn('some name', function() {
 *     // callback
 * });
 */
function memoize(fn, hasher = v => v) {
    var memo = Object.create(null);
    var queues = Object.create(null);
    var _fn = wrapAsync(fn);
    var memoized = initialParams((args, callback) => {
        var key = hasher(...args);
        if (key in memo) {
            setImmediate$1(() => callback(null, ...memo[key]));
        } else if (key in queues) {
            queues[key].push(callback);
        } else {
            queues[key] = [callback];
            _fn(...args, (err, ...resultArgs) => {
                // #1465 don't memoize if an error occurred
                if (!err) {
                    memo[key] = resultArgs;
                }
                var q = queues[key];
                delete queues[key];
                for (var i = 0, l = q.length; i < l; i++) {
                    q[i](err, ...resultArgs);
                }
            });
        }
    });
    memoized.memo = memo;
    memoized.unmemoized = fn;
    return memoized;
}

/* istanbul ignore file */

/**
 * Calls `callback` on a later loop around the event loop. In Node.js this just
 * calls `process.nextTick`.  In the browser it will use `setImmediate` if
 * available, otherwise `setTimeout(callback, 0)`, which means other higher
 * priority events may precede the execution of `callback`.
 *
 * This is used internally for browser-compatibility purposes.
 *
 * @name nextTick
 * @static
 * @memberOf module:Utils
 * @method
 * @see [async.setImmediate]{@link module:Utils.setImmediate}
 * @category Util
 * @param {Function} callback - The function to call on a later loop around
 * the event loop. Invoked with (args...).
 * @param {...*} args... - any number of additional arguments to pass to the
 * callback on the next tick.
 * @example
 *
 * var call_order = [];
 * async.nextTick(function() {
 *     call_order.push('two');
 *     // call_order now equals ['one','two']
 * });
 * call_order.push('one');
 *
 * async.setImmediate(function (a, b, c) {
 *     // a, b, and c equal 1, 2, and 3
 * }, 1, 2, 3);
 */
var _defer$1;

if (hasNextTick) {
    _defer$1 = process.nextTick;
} else if (hasSetImmediate) {
    _defer$1 = setImmediate;
} else {
    _defer$1 = fallback;
}

var nextTick = wrap(_defer$1);

var parallel = awaitify((eachfn, tasks, callback) => {
    var results = isArrayLike(tasks) ? [] : {};

    eachfn(tasks, (task, key, taskCb) => {
        wrapAsync(task)((err, ...result) => {
            if (result.length < 2) {
                [result] = result;
            }
            results[key] = result;
            taskCb(err);
        });
    }, err => callback(err, results));
}, 3);

/**
 * Run the `tasks` collection of functions in parallel, without waiting until
 * the previous function has completed. If any of the functions pass an error to
 * its callback, the main `callback` is immediately called with the value of the
 * error. Once the `tasks` have completed, the results are passed to the final
 * `callback` as an array.
 *
 * **Note:** `parallel` is about kicking-off I/O tasks in parallel, not about
 * parallel execution of code.  If your tasks do not use any timers or perform
 * any I/O, they will actually be executed in series.  Any synchronous setup
 * sections for each task will happen one after the other.  JavaScript remains
 * single-threaded.
 *
 * **Hint:** Use [`reflect`]{@link module:Utils.reflect} to continue the
 * execution of other tasks when a task fails.
 *
 * It is also possible to use an object instead of an array. Each property will
 * be run as a function and the results will be passed to the final `callback`
 * as an object instead of an array. This can be a more readable way of handling
 * results from {@link async.parallel}.
 *
 * @name parallel
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @category Control Flow
 * @param {Array|Iterable|AsyncIterable|Object} tasks - A collection of
 * [async functions]{@link AsyncFunction} to run.
 * Each async function can complete with any number of optional `result` values.
 * @param {Function} [callback] - An optional callback to run once all the
 * functions have completed successfully. This function gets a results array
 * (or object) containing all the result arguments passed to the task callbacks.
 * Invoked with (err, results).
 * @returns {Promise} a promise, if a callback is not passed
 *
 * @example
 *
 * //Using Callbacks
 * async.parallel([
 *     function(callback) {
 *         setTimeout(function() {
 *             callback(null, 'one');
 *         }, 200);
 *     },
 *     function(callback) {
 *         setTimeout(function() {
 *             callback(null, 'two');
 *         }, 100);
 *     }
 * ], function(err, results) {
 *     console.log(results);
 *     // results is equal to ['one','two'] even though
 *     // the second function had a shorter timeout.
 * });
 *
 * // an example using an object instead of an array
 * async.parallel({
 *     one: function(callback) {
 *         setTimeout(function() {
 *             callback(null, 1);
 *         }, 200);
 *     },
 *     two: function(callback) {
 *         setTimeout(function() {
 *             callback(null, 2);
 *         }, 100);
 *     }
 * }, function(err, results) {
 *     console.log(results);
 *     // results is equal to: { one: 1, two: 2 }
 * });
 *
 * //Using Promises
 * async.parallel([
 *     function(callback) {
 *         setTimeout(function() {
 *             callback(null, 'one');
 *         }, 200);
 *     },
 *     function(callback) {
 *         setTimeout(function() {
 *             callback(null, 'two');
 *         }, 100);
 *     }
 * ]).then(results => {
 *     console.log(results);
 *     // results is equal to ['one','two'] even though
 *     // the second function had a shorter timeout.
 * }).catch(err => {
 *     console.log(err);
 * });
 *
 * // an example using an object instead of an array
 * async.parallel({
 *     one: function(callback) {
 *         setTimeout(function() {
 *             callback(null, 1);
 *         }, 200);
 *     },
 *     two: function(callback) {
 *         setTimeout(function() {
 *             callback(null, 2);
 *         }, 100);
 *     }
 * }).then(results => {
 *     console.log(results);
 *     // results is equal to: { one: 1, two: 2 }
 * }).catch(err => {
 *     console.log(err);
 * });
 *
 * //Using async/await
 * async () => {
 *     try {
 *         let results = await async.parallel([
 *             function(callback) {
 *                 setTimeout(function() {
 *                     callback(null, 'one');
 *                 }, 200);
 *             },
 *             function(callback) {
 *                 setTimeout(function() {
 *                     callback(null, 'two');
 *                 }, 100);
 *             }
 *         ]);
 *         console.log(results);
 *         // results is equal to ['one','two'] even though
 *         // the second function had a shorter timeout.
 *     }
 *     catch (err) {
 *         console.log(err);
 *     }
 * }
 *
 * // an example using an object instead of an array
 * async () => {
 *     try {
 *         let results = await async.parallel({
 *             one: function(callback) {
 *                 setTimeout(function() {
 *                     callback(null, 1);
 *                 }, 200);
 *             },
 *            two: function(callback) {
 *                 setTimeout(function() {
 *                     callback(null, 2);
 *                 }, 100);
 *            }
 *         });
 *         console.log(results);
 *         // results is equal to: { one: 1, two: 2 }
 *     }
 *     catch (err) {
 *         console.log(err);
 *     }
 * }
 *
 */
function parallel$1(tasks, callback) {
    return parallel(eachOf$1, tasks, callback);
}

/**
 * The same as [`parallel`]{@link module:ControlFlow.parallel} but runs a maximum of `limit` async operations at a
 * time.
 *
 * @name parallelLimit
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @see [async.parallel]{@link module:ControlFlow.parallel}
 * @category Control Flow
 * @param {Array|Iterable|AsyncIterable|Object} tasks - A collection of
 * [async functions]{@link AsyncFunction} to run.
 * Each async function can complete with any number of optional `result` values.
 * @param {number} limit - The maximum number of async operations at a time.
 * @param {Function} [callback] - An optional callback to run once all the
 * functions have completed successfully. This function gets a results array
 * (or object) containing all the result arguments passed to the task callbacks.
 * Invoked with (err, results).
 * @returns {Promise} a promise, if a callback is not passed
 */
function parallelLimit(tasks, limit, callback) {
    return parallel(eachOfLimit(limit), tasks, callback);
}

/**
 * A queue of tasks for the worker function to complete.
 * @typedef {Iterable} QueueObject
 * @memberOf module:ControlFlow
 * @property {Function} length - a function returning the number of items
 * waiting to be processed. Invoke with `queue.length()`.
 * @property {boolean} started - a boolean indicating whether or not any
 * items have been pushed and processed by the queue.
 * @property {Function} running - a function returning the number of items
 * currently being processed. Invoke with `queue.running()`.
 * @property {Function} workersList - a function returning the array of items
 * currently being processed. Invoke with `queue.workersList()`.
 * @property {Function} idle - a function returning false if there are items
 * waiting or being processed, or true if not. Invoke with `queue.idle()`.
 * @property {number} concurrency - an integer for determining how many `worker`
 * functions should be run in parallel. This property can be changed after a
 * `queue` is created to alter the concurrency on-the-fly.
 * @property {number} payload - an integer that specifies how many items are
 * passed to the worker function at a time. only applies if this is a
 * [cargo]{@link module:ControlFlow.cargo} object
 * @property {AsyncFunction} push - add a new task to the `queue`. Calls `callback`
 * once the `worker` has finished processing the task. Instead of a single task,
 * a `tasks` array can be submitted. The respective callback is used for every
 * task in the list. Invoke with `queue.push(task, [callback])`,
 * @property {AsyncFunction} unshift - add a new task to the front of the `queue`.
 * Invoke with `queue.unshift(task, [callback])`.
 * @property {AsyncFunction} pushAsync - the same as `q.push`, except this returns
 * a promise that rejects if an error occurs.
 * @property {AsyncFunction} unshiftAsync - the same as `q.unshift`, except this returns
 * a promise that rejects if an error occurs.
 * @property {Function} remove - remove items from the queue that match a test
 * function.  The test function will be passed an object with a `data` property,
 * and a `priority` property, if this is a
 * [priorityQueue]{@link module:ControlFlow.priorityQueue} object.
 * Invoked with `queue.remove(testFn)`, where `testFn` is of the form
 * `function ({data, priority}) {}` and returns a Boolean.
 * @property {Function} saturated - a function that sets a callback that is
 * called when the number of running workers hits the `concurrency` limit, and
 * further tasks will be queued.  If the callback is omitted, `q.saturated()`
 * returns a promise for the next occurrence.
 * @property {Function} unsaturated - a function that sets a callback that is
 * called when the number of running workers is less than the `concurrency` &
 * `buffer` limits, and further tasks will not be queued. If the callback is
 * omitted, `q.unsaturated()` returns a promise for the next occurrence.
 * @property {number} buffer - A minimum threshold buffer in order to say that
 * the `queue` is `unsaturated`.
 * @property {Function} empty - a function that sets a callback that is called
 * when the last item from the `queue` is given to a `worker`. If the callback
 * is omitted, `q.empty()` returns a promise for the next occurrence.
 * @property {Function} drain - a function that sets a callback that is called
 * when the last item from the `queue` has returned from the `worker`. If the
 * callback is omitted, `q.drain()` returns a promise for the next occurrence.
 * @property {Function} error - a function that sets a callback that is called
 * when a task errors. Has the signature `function(error, task)`. If the
 * callback is omitted, `error()` returns a promise that rejects on the next
 * error.
 * @property {boolean} paused - a boolean for determining whether the queue is
 * in a paused state.
 * @property {Function} pause - a function that pauses the processing of tasks
 * until `resume()` is called. Invoke with `queue.pause()`.
 * @property {Function} resume - a function that resumes the processing of
 * queued tasks when the queue is paused. Invoke with `queue.resume()`.
 * @property {Function} kill - a function that removes the `drain` callback and
 * empties remaining tasks from the queue forcing it to go idle. No more tasks
 * should be pushed to the queue after calling this function. Invoke with `queue.kill()`.
 *
 * @example
 * const q = async.queue(worker, 2)
 * q.push(item1)
 * q.push(item2)
 * q.push(item3)
 * // queues are iterable, spread into an array to inspect
 * const items = [...q] // [item1, item2, item3]
 * // or use for of
 * for (let item of q) {
 *     console.log(item)
 * }
 *
 * q.drain(() => {
 *     console.log('all done')
 * })
 * // or
 * await q.drain()
 */

/**
 * Creates a `queue` object with the specified `concurrency`. Tasks added to the
 * `queue` are processed in parallel (up to the `concurrency` limit). If all
 * `worker`s are in progress, the task is queued until one becomes available.
 * Once a `worker` completes a `task`, that `task`'s callback is called.
 *
 * @name queue
 * @static
 * @memberOf module:ControlFlow
 * @method
 * @category Control Flow
 * @param {AsyncFunction} worker - An async function for processing a queued task.
 * If you want to handle errors from an individual task, pass a callback to
 * `q.push()`. Invoked with (task, callback).
 * @param {number} [concurrency=1] - An `integer` for determining how many
 * `worker` functions should be run in parallel.  If omitted, the concurrency
 * defaults to `1`.  If the concurrency is `0`, an error is thrown.
 * @returns {module:ControlFlow.QueueObject} A queue object to manage the tasks. Callbacks can be
 * attached as certain properties to listen for specific events during the
 * lifecycle of the queue.
 * @example
 *
 * // create a queue object with concurrency 2
 * var q = async.queue(function(task, callback) {
 *     console.log('hello ' + task.name);
 *     callback();
 * }, 2);
 *
 * // assign a callback
 * q.drain(function() {
 *     console.log('all items have been processed');
 * });
 * // or await the end
 * await q.drain()
 *
 * // assign an error callback
 * q.error(function(err, task) {
 *     console.error('task experienced an error');
 * });
 *
 * // add some items to the queue
 * q.push({name: 'foo'}, function(err) {
 *     console.log('finished processing foo');
 * });
 * // callback is optional
 * q.push({name: 'bar'});
 *
 * // add some items to the queue (batch-wise)
 * q.push([{name: 'baz'},{name: 'bay'},{name: 'bax'}], function(err) {
 *     console.log('finished processing item');
 * });