can't use Object.create to create object inside an object in javascript

Question

Let's say I have the following code:

(function($) {
    var Obj = {
        init: function() {
            var c1 = Object.create(this.MyChild);
            var c2 = Object.create(this.MyChild);
            c1.init(); //not working!!!
        },
        MyChild: function() {
            this.init = function() {
                console.log('calling MyChild init function');   
            }
        }
    };

    Obj.init();
})(jQuery);

When creating Obj, I used object literal as I don't need to create the instance of it, and when creating MyChild objects, I used the constructor function and used Object.create as I need to create multiple instances of MyChild.

However, when I call Object.create, it doesn't work, when c1.init() is called, it says the init function is undefined, but if I replaced Object.create(this.MyChild) to:

var c1 = new this.MyChild(); 
c1.init();

why?

`Object.create` is *not* a replacement for `new`! What's wrong with calling the constructor? — Bergi, Jan 15 '14 at 19:28
@Bergi I thought they are pretty much the same, it's just I have read some articles saying that "Object.create" should be used when creating the instance, instead of using "new". I think I'll just stick with var c1 = new this.MyChild(); — Josh, Jan 15 '14 at 20:09
Screw those articles. You can use `Object.create` when you don't need initialisation, and you should use it when you must not use initialisation. Maybe have a look at http://stackoverflow.com/a/11253826/1048572, http://stackoverflow.com/a/14267886/1048572 or http://stackoverflow.com/q/10898786/1048572 — Bergi, Jan 15 '14 at 20:16

score 1 · Answer 1 · answered Jan 15 '14 at 19:15

1

I think you should use

var c1 = Object.create(this.MyChild.prototype);

instead of

var c1 = Object.create(this.MyChild);

answered Jan 15 '14 at 19:15

S. A.

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Still, it would not have an `init` method then. – Bergi Jan 15 '14 at 19:28

basilikum · Accepted Answer · 2014-01-15T19:38:10.540

Object.create(func) doesn't do the same thing as new func()!

Object.create() creates an (otherwise empty!) object, which prototype will be set to the object, that is passed to that function (MDN)

To use Object.create() in your example, you could modify it like this:

(function($) {
    var Obj = {
        init: function() {
            var c1 = Object.create(this.MyChild);
            var c2 = Object.create(this.MyChild);
            c1.init(); //not working!!!
        },
        MyChild: {
            init: function() {
                console.log('calling MyChild init function');   
            }
        }
    };

    Obj.init();
})(jQuery);

But in this case everything will just POINT to your MyChild object. Properties of MyChild will be shared among every object, that you create using Object.create().

@cookiemonster: The constructor function into what is appropriate here. +1 — Bergi, Jan 15 '14 at 19:36
@Bergi: Yeah, I see it now. I was focused on the first `init`. Though the constructor isn't what changed. — cookie monster, Jan 15 '14 at 19:37

can't use Object.create to create object inside an object in javascript

2 Answers2