Async Auto Method

Migrated auto of Async to be standalone.

by andypotanin

JavaScript

//// cross-browser compatiblity functions ////

    var _each = function (arr, iterator) {
        if (arr.forEach) {
            return arr.forEach(iterator);
        }
        for (var i = 0; i < arr.length; i += 1) {
            iterator(arr[i], i, arr);
        }
    };

    var _map = function (arr, iterator) {
        if (arr.map) {
            return arr.map(iterator);
        }
        var results = [];
        _each(arr, function (x, i, a) {
            results.push(iterator(x, i, a));
        });
        return results;
    };

    var _reduce = function (arr, iterator, memo) {
        if (arr.reduce) {
            return arr.reduce(iterator, memo);
        }
        _each(arr, function (x, i, a) {
            memo = iterator(memo, x, i, a);
        });
        return memo;
    };

    var _keys = function (obj) {
        if (Object.keys) {
            return Object.keys(obj);
        }
        var keys = [];
        for (var k in obj) {
            if (obj.hasOwnProperty(k)) {
                keys.push(k);
            }
        }
        return keys;
    };

var auto = function (tasks, callback) {
        callback = callback || function () {};
        var keys = _keys(tasks);
        if (!keys.length) {
            return callback(null);
        }

        var results = {};

        var listeners = [];
        var addListener = function (fn) {
            listeners.unshift(fn);
        };
        var removeListener = function (fn) {
            for (var i = 0; i < listeners.length; i += 1) {
                if (listeners[i] === fn) {
                    listeners.splice(i, 1);
                    return;
                }
            }
        };
        var taskComplete = function () {
            _each(listeners.slice(0), function (fn) {
                fn();
            });
        };

        addListener(function () {
            if (_keys(results).length === keys.length) {
                callback(null, results);
                callback =...