An "extend" operator is a natural companion to <|

Brendan Eich brendan at
Tue Jul 19 12:44:22 PDT 2011

On Jul 19, 2011, at 12:05 PM, Allen Wirfs-Brock wrote:

>> Good point, though it does open the should-constructor-objects-inherit can of worms.
> Yes, but it is a can that needs to be emptied.

I agree. Other than "Java didn't have class-side inheritance and I did not miss it", I haven't heard a good reason to exclude it.

>> I'm not sure how effective it is to try to inherit constructor-like functions. If you're using inheritance, that implies to me that the derived object adds its own state that needs proper initialization. Given that, I worry that it would be more trouble than it's worth to define methods in base objects that can somehow anticipate that.
> This is a primary use case for class-side inheritance in Smalltalk. The collection class hierarchy is one place you can see their usage. Some design thought is usually required for inheritance to be effective as an an extension mechanism.  This applies whether you are on the class side or instance side.  The reason and patterns for using 'this' as opposed to a fixed value are the same on both sides.

And we've heard from Rubyists such as Yehuda Katz on this point.

>> The main point is that to do the right think here it is important to not think of it as being just like C++/C#/Java
>> Absolutely right. I don't want to turn JS into Java (ugh), and I don't think anyone else does either. I do think JS isn't as far from other OOP languages as it might like to believe, and we can occasionally use that to our advantage.
> I actually think JS is very far from class-as-static-nominal-type OOP languages.  It is quite close to other dynamic OOPP languages.  The exemplars we need to be look at are  Smalltalk, Ruby, and Python.

Don't forget Self :-P.

The functional programming (Scheme in spirit if not flesh) inspiration i took for JS also influences API design, avoiding silly single-method objects where functions will do.


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