Inheritance in Javascript via closure

Question

I'm attempting to learn Javascript inheritance and I've read some resources

on Stack Overflow about inheriting objects in Javascript to get started.

My goal is hiding private members from outside and I tought that the Closure way of inheriting and creating objects, even if it is not very memory friendly, might help me so I came up with this code:

"use strict";

//State is 'saved' by the closure capturing the value
var Contact = function(address)
{
  this.setAddressTo = function(newAddress)
  {
    address = newAddress;
  };

  this.getAddress = function()
  {
    return address;
  }
};

var Person = function(name, surname, address)
{
  //Superclass 'constructor' which will inherit everything public
  Contact.call(this, address);

  //Subclass members
  this.getName = function()
  {
    return name;
  };

  this.setName = function(newName)
  {
    name = newName;
  };

  this.getSurname = function()
  {
    return surname;
  };

  this.setName = function(newSurname)
  {
    surname = newSurname;
  };

  //Also with the prototype chaining I can access superclass methods
  this.setAddressTo = function(newAddress)
  {
      console.log('Setting address from base class');

      Person.prototype.setAddressTo(newAddress);
  }
}

Person.prototype = Object.create(Contact.prototype);

var p1 = new Person('#1.Name', '#1.Surname', '#1.Address');
var p2 = new Person('#2.Name', '#2.Surname', '#2.Address');

console.log('P1 is a person ? ' + (p1 instanceof Person)); //Yes
console.log('P1 is a contact ? ' + (p1 instanceof Contact)); //Yes

console.log('P2 is a person ? ' + (p2 instanceof Person)); //Yes
console.log('P2 is a contact ? ' + (p2 instanceof Contact)); //Yes

console.log(p1.getAddress()); //'#1.Address'
console.log(p2.getAddress()); //'#1.Address'

p1.setAddressTo('#1.Other_Address');
p2.setAddressTo('#2.Other_Address');

console.log(p1.getAddress()); //'#1.Other_Address'
console.log(p2.getAddress()); //'#2.Other_Address'

//Should be undefined because it is not accesible
console.log(p1.address);
console.log(p2.address);

The line:

Person.prototype = Object.create(Contact.prototype);

I use it for making the 'instanceof' operator working correctly (which means that a Person object is an instance of Person and Contact)

Is it correct to do this ?

These lines:

var p1 = new Person('#1.Name', '#1.Surname', '#1.Address');
var p2 = new Person('#2.Name', '#2.Surname', '#2.Address');

Is correct calling the function Person() with 'new' ?

To me it makes sense because I will receive a new Object with its prototype set to Person.prototype which has its prototype set to Contact.prototype (I guess) and this will make the newly created object effectively a Person.

The approach that I've posted is valid to achieve inheritance correctly in Javascript or other better best practices exists to achieve the same thing ?

if you don't call `new Person(...)` p1 will be undefined, and you will have `TypeError` when calling `p1.getAddress()`, unless you'll add `return this;` at the end of the `Person` function — , Jul 15 '15 at 13:04
Yes indeed, you are right. I've should have been more specific and should have added that to use the function without the 'new' operator it should have a 'return' statement. — Gwinn, Jul 15 '15 at 13:10
Yes, you have implemented inheritance. Yes, it is correct to use `new Person()`. Yes, the storage of the `address` property is private in a closure. Beyond that, I really can't tell what you're asking. This almost sounds like a request for code review on working code. Is there more to your question? FYI, an age-old tutorial on private member variables is here: http://javascript.crockford.com/private.html. — jfriend00, Jul 16 '15 at 03:54
Well basically the question is if it is can be considered correct in Javascript or there are different and better practices to achieve the same result. Anyway, thank you for your response — Gwinn, Jul 16 '15 at 06:04

Inheritance in Javascript via closure

0 Answers0