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

node_modules/async/foldr.js

@@ -0,0 +1,44 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = reduceRight;
+
+var _reduce = require('./reduce');
+
+var _reduce2 = _interopRequireDefault(_reduce);
+
+var _slice = require('./internal/slice');
+
+var _slice2 = _interopRequireDefault(_slice);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+/**
+ * Same as [`reduce`]{@link module:Collections.reduce}, only operates on `array` in reverse order.
+ *
+ * @name reduceRight
+ * @static
+ * @memberOf module:Collections
+ * @method
+ * @see [async.reduce]{@link module:Collections.reduce}
+ * @alias foldr
+ * @category Collection
+ * @param {Array} array - 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).
+ */
+function reduceRight(array, memo, iteratee, callback) {
+  var reversed = (0, _slice2.default)(array).reverse();
+  (0, _reduce2.default)(reversed, memo, iteratee, callback);
+}
+module.exports = exports['default'];