'use strict';
var eachOfSeries = require('async.eachofseries');
module.exports = function reduce(arr, memo, iterator, cb) {
eachOfSeries(arr, function(x, i, cb) {
iterator(memo, x, function(err, v) {
memo = v;
cb(err);
});
}, function(err) {
cb(err, memo);
});
};