Improve code quality and write tests

node_modules/regexp-tree/dist/utils/clone.js

@@ -0,0 +1,29 @@
+/**
+ * The MIT License (MIT)
+ * Copyright (c) 2017-present Dmitry Soshnikov <dmitry.soshnikov@gmail.com>
+ */
+
+'use strict';
+
+/**
+ * Performs a deep copy of an simple object.
+ * Only handles scalar values, arrays and objects.
+ *
+ * @param obj Object
+ */
+
+module.exports = function clone(obj) {
+  if (obj === null || typeof obj !== 'object') {
+    return obj;
+  }
+  var res = void 0;
+  if (Array.isArray(obj)) {
+    res = [];
+  } else {
+    res = {};
+  }
+  for (var i in obj) {
+    res[i] = clone(obj[i]);
+  }
+  return res;
+};