"Privates" in JS

pijs.js

// Defining "private" properties in JavaScript

// define youre own scope by using an
// immediate executed function
(function (){

	// x is only be visible within this scope a.k.a this function
	var x = null;

	var Bla = function(blup) {
		// x is visible here
	    x = blup;
	};

	Bla.prototype.on = function() {
	 		// x is visible here
	        alert(x);
	};

}());

// x is not visible here
console.log(typeof x === 'undefined'); // true