Function _reduce

public/javascripts/async.js:104–109

(arr, iterator, memo)

    }

    function _reduce(arr, iterator, memo) {
        _arrayEach(arr, function (x, i, a) {
            memo = iterator(memo, x, i, a);
        });
        return memo;
    }

    function _forEachOf(object, iterator) {
        _arrayEach(_keys(object), function (key) {