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

node_modules/async/groupBy.js

@@ -0,0 +1,54 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+
+var _doLimit = require('./internal/doLimit');
+
+var _doLimit2 = _interopRequireDefault(_doLimit);
+
+var _groupByLimit = require('./groupByLimit');
+
+var _groupByLimit2 = _interopRequireDefault(_groupByLimit);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+/**
+ * Returns a new object, where each value corresponds to an array of items, from
+ * `coll`, that returned the corresponding key. That is, the keys of the object
+ * correspond to the values passed to the `iteratee` callback.
+ *
+ * Note: Since this function applies the `iteratee` to each item in parallel,
+ * there is no guarantee that the `iteratee` functions will complete in order.
+ * However, the values for each key in the `result` will be in the same order as
+ * the original `coll`. For Objects, the values will roughly be in the order of
+ * the original Objects' keys (but this can vary across JavaScript engines).
+ *
+ * @name groupBy
+ * @static
+ * @memberOf module:Collections
+ * @method
+ * @category Collection
+ * @param {Array|Iterable|Object} coll - A collection to iterate over.
+ * @param {AsyncFunction} iteratee - An async function to apply to each item in
+ * `coll`.
+ * The iteratee should complete with a `key` to group the value under.
+ * Invoked with (value, callback).
+ * @param {Function} [callback] - A callback which is called when all `iteratee`
+ * functions have finished, or an error occurs. Result is an `Object` whoses
+ * properties are arrays of values which returned the corresponding key.
+ * @example
+ *
+ * async.groupBy(['userId1', 'userId2', 'userId3'], function(userId, callback) {
+ *     db.findById(userId, function(err, user) {
+ *         if (err) return callback(err);
+ *         return callback(null, user.age);
+ *     });
+ * }, function(err, result) {
+ *     // result is object containing the userIds grouped by age
+ *     // e.g. { 30: ['userId1', 'userId3'], 42: ['userId2']};
+ * });
+ */
+exports.default = (0, _doLimit2.default)(_groupByLimit2.default, Infinity);
+module.exports = exports['default'];