gistfile1.js

// crockford problem
(function(){console.log('module1');}())(function(){console.log('module2');}());
// => module1
// => module2
// => TypeError: undefined is not a function

// it invokes module1
(function(){ console.log('module1'); }())
// => module1

//it invokes module2
(function(){ console.log('module2'); }());
// => module2

// equivalent
(undefined(undefined))
// => TypeError: undefined is not a function