JS Revealing Module private variable value issue

I've got stuck with this issue.

var myModule = (function(){

    var foo;

    foo = "bab"; 
    console.log(foo);

    foo = "bab" + "more";
    console.log(foo);


    function mth1(){
      foo = "mag";
      console.log(foo);
    }

    return{
      pubMethod1: mth1 
    };

})();

myModule.pubMethod1();

The problem is that instead of this output:

"bab"
"bab more"
"mag"

I get this output:

"bab"
"mag"
"mag"

More specifically, the "bab more" is for some reason overwritten by mth1() value.

Original code publishing is not available.

Your thoughts much appreciated.