add eslint and clean up code

src/scripts/lib/utils.js

@@ -0,0 +1,18 @@
+'use strict';
+
+/**
+ * Batch update all the properties of an object.
+ * @param {object} obj
+ * @param {object} descriptor
+ * @param {boolean} [descriptor.configurable]
+ * @param {boolean} [descriptor.enumerable]
+ * @param {*} [descriptor.value]
+ * @param {boolean} [descriptor.writable]
+ * @param {function} [descriptor.get]
+ * @param {function} [descriptor.set]
+ */
+module.exports.updateProperties = function(obj, descriptor) {
+  Object.getOwnPropertyNames(obj).forEach(function(prop) {
+    Object.defineProperty(obj, prop, descriptor);
+  });
+};