Inheritance from one instance in javascript

Question

I want to know if it's possible having something like this:

basic class A
derived class B1 from one instance a of class A (i.e. a = new A() )
derived class B2 from same instance a of A

I give an example:

var a = new A();
function A() {
    this.var_test = 0;
    this.test = function () {
        alert(this.var_test++);
    }
}

function B1() {
}
B1.prototype = a;

function B2() {         
}
B2.prototype = a;

var b1 = new B1();
var b2 = new B2();
b1.test(); // i want alert(0)
b2.test(); // i want alert(1)

How to do it?

Emil S. Jørgensen · Accepted Answer · 2016-09-08 14:22:10Z

1

Sure, just use the standard methods for inheritance:

console.clear();
function A() {
  this.test = function() {
    alert(A.var_test++);
  }
  A.var_test = 0;
}
var a = new A();
b1 = Object.create(a);
b2 = Object.create(a);
b1.test();
b2.test();
b1.test();
b2.test();

edited Sep 8, 2016 at 14:22

answered Sep 8, 2016 at 14:13

Emil S. Jørgensen

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1 Comment

medvi_dinya Over a year ago

yeeeah, that's what i need! thank you for your example

Abraham Vegh · Accepted Answer · 2016-09-08 14:44:16Z

0

Here’s some recommended reading from Douglas Crockford on classical inheritance in JavaScript: http://javascript.crockford.com/inheritance.html

As he says, quite succinctly:

JavaScript is a class-free, object-oriented language, and as such, it uses prototypal inheritance instead of classical inheritance. This can be puzzling to programmers trained in conventional object-oriented languages like C++ and Java. JavaScript's prototypal inheritance has more expressive power than classical inheritance […]

answered Sep 8, 2016 at 14:44

Abraham Vegh

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