What's the difference between 2 JavaScript objects?

Question

I try do improve my JavaScript skills. I don't understand why (5) works and (2) returns error. Isn't the same?

1. B.fn() //OK
2. B.fn2() //TypeError: Object # has no method 'fn2'
3. var a = new A()
4. a.fn() //OK

5. a.fn2() //OK

   var A = function () {
       this.fn = function () { alert(3); }
   }
   A.prototype = {
       fn2: function () { alert(4); }
   };
   
   var B =
       {
           fn: function () { alert(1); }
       }
   B.prototype = {
       fn2: function () { alert(2); }
   };
   

Answer 1

a is an instance of the A class, where as B is the class itself. Since fn2 is not defined as static function, it will only be available to an instance of class B as opposed to the class B itself.

If you wanted to use B directly, you could use:

new B().fn2()

if you define B as a function()

Alternatively, you could define fn2 the same way you have defined fn