self_executing_functions.js

// Private Scope
(function ($) {
  var variable = "Hello";
}(jQuery));

alert(typeof variable); // undefined

// Private Scope, Public Variable
var variable = (function ($){
  var first = "Hel", second = "lo";
  return first + second;
}(jQuery));

alert(variable); // "Hello"
alert(typeof first);    // Undefined
alert(typeof second);   // Undefined