I have two objects with functions inside. And first works perfect, but second return error than "helper.calc.add is not a function". Whats wrong?

For example first: 

```
var calc = (function () {
    var add;
    var remove;

    // some functions add and remove...

   return {
    add: add,
    remove: remove
  }
})();

calc.add(1);

```

And second:

```
var helper = (function () {
   return {
        calc: function () {
           var add;
           var remove;

           // some functions add and remove...

           return {
              add: add,
              remove: remove
          }
       }
  }
})();

helper.calc.add(1);

```

In console:

```
1
Uncaught TypeError: helper.calc.add is not a function

```

Fiddle: <https://jsfiddle.net/pk4tsnnt/>