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

node_modules/async/groupByLimit.js

@@ -0,0 +1,71 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+
+exports.default = function (coll, limit, iteratee, callback) {
+    callback = callback || _noop2.default;
+    var _iteratee = (0, _wrapAsync2.default)(iteratee);
+    (0, _mapLimit2.default)(coll, limit, function (val, callback) {
+        _iteratee(val, function (err, key) {
+            if (err) return callback(err);
+            return callback(null, { key: key, val: val });
+        });
+    }, function (err, mapResults) {
+        var result = {};
+        // from MDN, handle object having an `hasOwnProperty` prop
+        var hasOwnProperty = Object.prototype.hasOwnProperty;
+
+        for (var i = 0; i < mapResults.length; i++) {
+            if (mapResults[i]) {
+                var key = mapResults[i].key;
+                var val = mapResults[i].val;
+
+                if (hasOwnProperty.call(result, key)) {
+                    result[key].push(val);
+                } else {
+                    result[key] = [val];
+                }
+            }
+        }
+
+        return callback(err, result);
+    });
+};
+
+var _noop = require('lodash/noop');
+
+var _noop2 = _interopRequireDefault(_noop);
+
+var _mapLimit = require('./mapLimit');
+
+var _mapLimit2 = _interopRequireDefault(_mapLimit);
+
+var _wrapAsync = require('./internal/wrapAsync');
+
+var _wrapAsync2 = _interopRequireDefault(_wrapAsync);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+;
+/**
+ * The same as [`groupBy`]{@link module:Collections.groupBy} but runs a maximum of `limit` async operations at a time.
+ *
+ * @name groupByLimit
+ * @static
+ * @memberOf module:Collections
+ * @method
+ * @see [async.groupBy]{@link module:Collections.groupBy}
+ * @category Collection
+ * @param {Array|Iterable|Object} coll - A collection to iterate over.
+ * @param {number} limit - The maximum number of async operations at a time.
+ * @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.
+ */
+module.exports = exports['default'];