Prototypal inheritance with function constructors

Question

If we assume that javascript uses two ways of building proper inheritance, with function constructors and keyword 'new', and pure prototypal inheritance with Object.create:

how can I make prototype chain by using exclusively function constructor method:

function Original() {
    this.name = 'John';
}
var copyOne = new Original();
copyOne.lastname = 'Doe';

var copyTwo = ?

Now, how can I build 'copyTwo' object that inherits both items from 'copyOne' and 'Original'. But items from copyOne object should be inside prototype of copyTwo, so that it is lighter on memory usage (as inherited objects all point to only one prototype instance, and don't have a copy of an item). I go to Chrome debugger and enter console.log(copyTwo) to see where those items are located in copyTwo object.

I am aware that this prototype chain can be built by using Object.create way, but I don't know how to mimic it with function constructors and 'new'.

Let's suppose that I don't want to use pure prototypal instance with using Object.create for building copyTwo.

Is there a way? Thanks.

Jonas Wilms · Accepted Answer · 2017-07-23 09:11:29Z

2

function Copy(){}
Copy.prototype = new Original;
Copy.prototype.lastname="doe";

var copyTwo = new Copy;

However, there are not two kinds of inheritance , js has prototypal inheritance and thats it.

And if you want light weight memory usage, dont set static props in the constructor but the prototype:

function Original() {   }

Original.prototype = { name:'John'};

edited Jul 23, 2017 at 9:11

answered Jul 23, 2017 at 9:03

Jonas Wilms

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2 Comments

Dan Over a year ago

So, every time I need to repeat this if I have more nested objects? For example if I have copyThree that I want to inherit from copyTwo, I need to repeat above code with: Copy2.prototype = new Copy. If that is so, I think it is easier to use inheritance with Object.create. Thanks a lot

Jonas Wilms Over a year ago

@Dan yes. thats why theres Object.create, and youre welcome ;)

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