Javascript syntax

http://braincracking.org/2011/11/16/javascript-3-fondamentaux/

• var to define a variable with a local scope
  var i = 1; create the i variable and its value is only available the first time, it's set. More precisely, this variable has its value inside the function it has been created, and in the function this function is calling, but not before.
  This way there'll not be variable collabpse. If ommited the variable scope is global.

test1 = function() {
	var x = 1;
	test2 = function() {
		var x = 2;
		test3 = function() {
			var x = 3;
			console.log(x); // 3
		}();
	}();
	console.log(x); // 1
}();
console.log(x); // undefined

• isolate the code
  To be sure not to have variable collapse always embed the code in

(function() { 
}()) 

In drupal it's

(function ($) {
...
})(jQuery);