from Hacker News

The Ways of Javascript Inheritance

by brittonrt on 3/2/13, 12:17 AM with 2 comments

Hey Hacker News! Lets talk about prototypal inheritance in JS!

What's the best way of doing it from a code reusability standpoint?

What's the best way of doing it from a time to create instance standpoint?

What's the best way of doing it from memory footprint standpoint?

Of the ways I've seen and tried, John's method seems the easiest to use: http://ejohn.org/blog/simple-javascript-inheritance/

But I hate that it has to loop through every property every time you extend a prototype.

Most inheritance patterns I've seen need to have the original prototype cloned or instantiated in order extend a new prototype safely. Is there a way to do it that allows all instances at all levels of the inheritance chain to still share the same common methods in memory where they aren't overridden?

Thanks!

by ricardobeat on 3/2/13, 3:25 AM
To cut the story short, there is basically a single way to do "proper" inheritance in javascript, which is Crockford's prototypal inheritance [1]. There are a dozen variations on it, here is one:
```
    function inherits (child, parent) {
        extend(child, parent)
        function Ctor () { this.constructor = child }
        Ctor.prototype = parent.prototype
        child.prototype = new Ctor()
        child.__super__ = parent.prototype
        return child
    }

    function Animal ...
    Animal.prototype.x = ...

    function Cat ...
 
    inherits(Cat, Animal)
```
See Backbone's implementation [2] for another example. This eventually morphed into the standard `Object.create` method [3], supported in IE9+.
[1] http://javascript.crockford.com/prototypal.html
[2] http://backbonejs.org/docs/backbone.html#section-186
[3] https://developer.mozilla.org/en-US/docs/JavaScript/Referenc...
by keefe on 3/5/13, 6:27 AM
I like something like jQuery.extend(true, {}, src)