immediately-invoked func­tion expres­sions(IIFE) http://tech.myemma.com/iifes-javascript-control-variable-scope/

iife.js

// Take con­trol of your globals

//basic
(function () {
     // your code here
})();

// pass param in
(function ($) {
  $(document).ready(function () {
    // my code
  });
})(jQuery);

// expose param out
var obj = (function () {
  return {
    methodA: ...
  }
})();
obj.methodA();