x in obj -> obj.hasOwnProperty(x)

lib/localStorage.js

@@ -15,7 +15,7 @@
   db = LocalStorage;
 
   db.prototype.getItem = function (key) {
-    if (key in this) {
+    if (this.hasOwnProperty(key)) {
       return String(this[key]);
     }
     return null;