Override constructor in the Object.create inheritance pattern

Question

I'd like a subclass' constructor to call it's parent's constructor before executing itself, with the Object.create pattern.

Using `new Parent()`

var Parent = function(){ console.log( 'Parent' ) };
var Child  = function(){ console.log( 'Child' ) };
Child.prototype = new Parent(); // Prints 'Parent'
var child = new Child(); // Prints 'Child'

Using `Object.create`

var Parent = function(){ console.log( 'Parent' ) };
var Child  = function(){ console.log( 'Child' ) };
Child.prototype = Object.create( Parent.prototype );
var child = new Child(); // I'd like this to print 'Parent' then 'Child'

Is this even possible? Can I add something like Parent.call( this ) in the Child constructor?

possible duplicate of Correct javascript inheritance

Bergi
– Bergi

2014-02-18 19:32:05 +00:00
Commented Feb 18, 2014 at 19:32 — Bergi
– Bergi, Commented Feb 18, 2014 at 19:32

Bergi · Accepted Answer · 2014-02-18 19:33:43Z

1

Can I add something like Parent.call( this ) in the Child constructor?

Yes, just do exactly this.

var Parent = function(){ console.log( 'Parent' ) };
var Child  = function(){ Parent.call(this); console.log( 'Child' ) };
Child.prototype = Object.create( Parent.prototype ); // should print nothing
var child = new Child(); // prints 'Parent' then 'Child'

answered Feb 18, 2014 at 19:33

Bergi

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Comments

Xenia Kramer · Accepted Answer · 2014-02-18 19:49:08Z

0

Great question. You already answered it, though.

var Parent = function(){console.log('Parent')};
var Child = function(){
  console.log('Child')
  Parent.call(this);
};
Child.prototype = new Parent();
var child = new Child();

in the Firebug console produces

Parent
Child
Parent
Object { }

as output.

answered Feb 18, 2014 at 19:49

Xenia Kramer

11 bronze badge

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