We discussed how to write classes in JavaScript earlier. Private implementations are not discussed. Check this one out.

We know that the implementation of private properties in JS is essentially var + closure. The following

function Person(n, a){
    // public
    this.name = n;
    // private
    var age = a;
    this.getName = function(){
        return this.name;
    }
    this.getAge = function(){
        return age;
    }
}

As shown in the test, age is private and cannot be obtained with the point operator, but only with the getName method.

var p = new Person('jack',23);
console.log(p.age);  // undefined
console.log(p.getAge()); // 23

This is nothing fancy, but let’s do it using a utility function.  

function $class(className, classImp){
    function clazz(){
        if(typeof this.init == "function"){
            this.init.apply(this, arguments);
        }
    }
    classImp.call(clazz.prototype);
    window[className] = clazz;
}

Write a class

$class('Person', function(){
    //Private properties are defined here
    var age = '';
    this.init = function(n, a){
        //The Shared property is hung on this, initialized
        this.name = n;
        //Private property initialization
        age = a;
    };
    this.getName = function(){
        return this.name;
    };
    this.getAge = function(){
        return age;
    }
});

New is an instance object

var p = new Person('jack',23);
console.log(p.name); //Jack common can be obtained using the point operator
console.log(p.age); //Undefined private cannot be obtained by the point operator
console.log(p.getAge()); //Private age can only be obtained through a Shared method called getAge