Merge pull request #1585 from lumosmind/patch-31

not proved features of class properties

1-js/09-classes/01-class/article.md

@@ -318,6 +318,9 @@ class User {
 }
 
 new User().sayHi();
+
+alert(User.prototype.sayHi); // placed in User.prototype
+alert(User.prototype.name); // undefined, not placed in User.prototype
 ```
 
 The property `name` is not placed into `User.prototype`. Instead, it is created by `new` before calling the constructor, it's a property of the object itself.