Why would one write global code inside a function definition-call pair?

Question

I see examples where JavaScript code including jQuery and jslint use the notation below:

(function(){
  // do something
})();

instead of:

Answer 1

It's about scope for functions, too - everything declared within the code block is scoped to that anonymous function only. Things are normally made public by the framework

(function($) {

  var localVarOnly = "local";

  $.fn.myCoolFunction = function() { // in the case of jquery, make this publicly available
    otherCoolFunction(); //alerts hi
    alert(localVarOnly); // alerts local
  };

  function otherCoolFunction() { // scoped to this anonymous function only
    alert('hi');
  };

})(jQuery);

otherCoolFunction(); // undefined
alert(localVarOnly); // undefined