var result = (function() {

  var f = function g() {

    return 1;

  };

​

  // g is only available within the expression.

  // g can call g within itself.

  // Adding parentheses makes it easier to visualize:

  var ff = (function gg() { return 1; });

​

  return g();

})();

​

console.log(result); // ReferenceError: g is not defined