OO – Encapsulation Example

by Joshua McNeese

JavaScript

// Define the Person constructor
function Person(name) {
    this.name = name;
};

// via closure
function StudentClosure(name, age) {

    var _age = age;

    Person.call(this, name);

    // to be able to have protoype methods that can access _age,
    // they have to be defined within the constructor's scope
    this.setAge = function (age) {
        _age = age;
    };
    this.getAge = function () {
        return _age;
    };

}

StudentClosure.prototype = Object.create(Person.prototype);
StudentClosure.prototype.constructor = StudentClosure;

// via IIFE
var StudentIIFE = (function () {

    var _age;

    // Define the Student constructor
    function StudentIIFE(name, age) {
        // Call the parent constructor function in own context
        Person.call(this, name);
        _age = age;
    };

    StudentIIFE.prototype = Object.create(Person.prototype);
    StudentIIFE.prototype.constructor = StudentIIFE;
    StudentIIFE.prototype.setAge = function (age) {
        _age = age;
    };
    StudentIIFE.prototype.getAge = function () {
        return _age;
    };

    return StudentIIFE;

}());

// Example usage:
var student1 = new StudentClosure("Janet", 24);
console.log('student1', student1);
student1.setAge(25);
console.log('student1.getAge()', student1.getAge());

var student2 = new StudentIIFE("Walter", 45);
console.log('student2', student2);
student2.setAge(46);
console.log('student2.getAge()', student2.getAge());