JavaScript: private, public, static methods and properties

JavaScript has its own way to define scoping of variables, properties and methods. Public properties and methods are declared with this.property1 and this.method1() in a function F1 (class). And all the var   declared variables are private and also as usual functions (function f1(), function f2() etc.) are private method.  You can add private, public and static methods as follows:

//constructor function (class)
function Maths(x, y) {
//public properties
this.x =x;
this.y = y;

//public methods
this.add = function () { _sum = x + y; return _sum; }
this.mod = function () { _mod = x % y; return _mod; }

//public method calls private method
this.show = function () {
this.add();
this.mod();
showResult();
}

//private variables
var _sum=0;
var _mod=0;

//private methods
function showResult() {
alert( "sum: " + _sum + ", mod: " + _mod );
}

}
//end function

//create instance
var plus = new Maths(3, 4);
plus.show();

//static method multiply, you can use it without instance of Maths
Maths.multiply = function (x,y) {  return x * y; }

//call static method by constructor function (class) without instance of Maths
var result = Maths.multiply(5,7);
alert(result);
//output: 35