Subj : Re: Array and [ ]
To   : netscape.public.mozilla.jseng
From : Jens Thiele
Date : Mon Jan 24 2005 12:31 am

Brendan Eich schrieb:
> although a subclass of Array might be more appropriate in a real application

what exactly do you mean with subclass here?
js2?

the only way i know to inherit from objects like Array (or in fact to
inherit [[class]] involves __proto__).

Example:
// "hack" for inheriting [[class]]

function assert(f) {
         if (!f()) throw "Assertion failed:"+f.toSource();
}

function Subarray() {
         var ret=Array();
         ret.__proto__=Subarray.prototype;
         return ret;
}

Subarray.prototype.foo=function(){return this.length;}
Subarray.prototype.__proto__=Array.prototype;

s=Subarray();
s[0]=s[1]=10;
print(s.foo());
assert(function(){return s.foo()==2;});
assert(function(){return s instanceof Subarray;});
assert(function(){return s instanceof Array;});


though I in fact like this
i also could imagine js without new and without .prototype
only having __proto__. I think this would make it more obvious how the
prototyping works and stop the confusion and wrong expectations.

Greetings
jens

.