added unit testing, and started implementing unit tests...phew

node_modules/async/foldl.js

@@ -0,0 +1,78 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+exports.default = reduce;
+
+var _eachOfSeries = require('./eachOfSeries');
+
+var _eachOfSeries2 = _interopRequireDefault(_eachOfSeries);
+
+var _noop = require('lodash/noop');
+
+var _noop2 = _interopRequireDefault(_noop);
+
+var _once = require('./internal/once');
+
+var _once2 = _interopRequireDefault(_once);
+
+var _wrapAsync = require('./internal/wrapAsync');
+
+var _wrapAsync2 = _interopRequireDefault(_wrapAsync);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+/**
+ * Reduces `coll` into a single value using an async `iteratee` to return each
+ * successive step. `memo` is the initial state of the reduction. This function
+ * only operates in series.
+ *
+ * For performance reasons, it may make sense to split a call to this function
+ * into a parallel map, and then use the normal `Array.prototype.reduce` on the
+ * results. This function is for situations where each step in the reduction
+ * needs to be async; if you can get the data before reducing it, then it's
+ * probably a good idea to do so.
+ *
+ * @name reduce
+ * @static
+ * @memberOf module:Collections
+ * @method
+ * @alias inject
+ * @alias foldl
+ * @category Collection
+ * @param {Array|Iterable|Object} coll - A collection to iterate over.
+ * @param {*} memo - The initial state of the reduction.
+ * @param {AsyncFunction} iteratee - A function applied to each item in the
+ * array to produce the next step in the reduction.
+ * The `iteratee` should complete with the next state of the reduction.
+ * If the iteratee complete with an error, the reduction is stopped and the
+ * main `callback` is immediately called with the error.
+ * Invoked with (memo, item, callback).
+ * @param {Function} [callback] - A callback which is called after all the
+ * `iteratee` functions have finished. Result is the reduced value. Invoked with
+ * (err, result).
+ * @example
+ *
+ * async.reduce([1,2,3], 0, function(memo, item, callback) {
+ *     // pointless async:
+ *     process.nextTick(function() {
+ *         callback(null, memo + item)
+ *     });
+ * }, function(err, result) {
+ *     // result is now equal to the last value of memo, which is 6
+ * });
+ */
+function reduce(coll, memo, iteratee, callback) {
+    callback = (0, _once2.default)(callback || _noop2.default);
+    var _iteratee = (0, _wrapAsync2.default)(iteratee);
+    (0, _eachOfSeries2.default)(coll, function (x, i, callback) {
+        _iteratee(memo, x, function (err, v) {
+            memo = v;
+            callback(err);
+        });
+    }, function (err) {
+        callback(err, memo);
+    });
+}
+module.exports = exports['default'];