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

node_modules/async/internal/iterator.js

@@ -0,0 +1,58 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+exports.default = iterator;
+
+var _isArrayLike = require('lodash/isArrayLike');
+
+var _isArrayLike2 = _interopRequireDefault(_isArrayLike);
+
+var _getIterator = require('./getIterator');
+
+var _getIterator2 = _interopRequireDefault(_getIterator);
+
+var _keys = require('lodash/keys');
+
+var _keys2 = _interopRequireDefault(_keys);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+function createArrayIterator(coll) {
+    var i = -1;
+    var len = coll.length;
+    return function next() {
+        return ++i < len ? { value: coll[i], key: i } : null;
+    };
+}
+
+function createES2015Iterator(iterator) {
+    var i = -1;
+    return function next() {
+        var item = iterator.next();
+        if (item.done) return null;
+        i++;
+        return { value: item.value, key: i };
+    };
+}
+
+function createObjectIterator(obj) {
+    var okeys = (0, _keys2.default)(obj);
+    var i = -1;
+    var len = okeys.length;
+    return function next() {
+        var key = okeys[++i];
+        return i < len ? { value: obj[key], key: key } : null;
+    };
+}
+
+function iterator(coll) {
+    if ((0, _isArrayLike2.default)(coll)) {
+        return createArrayIterator(coll);
+    }
+
+    var iterator = (0, _getIterator2.default)(coll);
+    return iterator ? createES2015Iterator(iterator) : createObjectIterator(coll);
+}
+module.exports = exports['default'];