gistfile1.js

function named(){
  (function(){
    this.foo = function() {
      alert('bar');
    }
  })();
}

named.foo();

function named(){
  (function(){
    this.foo = function() {
      alert('bar');
    }
  })();
}
// calling named causes the interior IIFE to be invoked, but `this` is window in this context.
named()

// at this point `foo` has been exported to window and can be called
foo()

// calling `named()` with this will return an object which has the `foo` function as a member
function named(){
  this.foo = function() {
    alert('bar');
  }
  return this;
}

named().foo()