Revealing Module Design Pattern

design_pattren.js

/**
 * 
 * @param {number} x 
 * @param {number} y 
 * 
 * @returns function
 */
var Calculator = (function(){
    var _privateVariable = 100;
    
    //Private function 
    function _privateFunction(x, y){
        return (x*x) + (y *y);
    }
    function sum(x, y){
        return x + y;
    }
    function mul(x, y){
        return x * y;
    }
    function divide(x, y){
        return x / y;
    }
    function square(x, y) {     
        return _privateFunction(x, y);
    }
    // functions are revelied here
    return {
        sum : sum,
        mul : mul,
        divide : divide,
        square: square
    }
})();

var cal = Calculator;
console.log(cal.sum(2,3));
console.log(cal.mul(2,3));
console.log(cal.divide(2,3));
console.log(cal.square(2,3));