On Tuesday 10 March 2009 14:06:17 kangax wrote:
> > > > > It's possible that we'll introduce a custom `hasOwnProperty` in
> > > > > later revisions.
> > > >
> > > > Makes sense.
> > > > if( !hasOwnProperty )
> > > > hasOwnProperty = function hasOwnProperty(){ ... };
> > >
> > > I was thinking of something like:
> > >
> > > var hasOwnProperty = (function(){
> > > var hop = Object.prototype.hasOwnProperty;
> > > if (hop) {
> > > return function(obj, prop) {
> > > return hop.call(obj, prop);
> > > }
> > > }
> >
> > Why not:
> > if( hop )
> > return hop;
> >
> > Does hop need to be wrapped?
>
> Writing `hasOwnProperty.call(object, property)` is a bit tedious. Why
> not just encapsulate the `call`?
Ah, yes, I imagined we'd be adding hasOwnProperty to Object.prototype to make
the bad browsers like the good. Given the subject, probably not wise :-)
> > > return function(obj, prop) {
> > > if (obj) {
> > > var c = obj.constructor;
> > > if (c && c.prototype) {
> > > return obj[prop] !== c.prototype[prop];
> > > }
> > > }
> > > return null;
> > > }
> > > })();
> > >
> > > This fallback not bullet-proof, but should cover most of the cases.
> >
> > Yep, the tragic case where something just happens to have a property in a
> > prototype *and* the same property directly - could happen! Still, I think
> > the code above would be fine for almost all cases.
>
> Another edge case is when an object does not expose (think host
> objects in MSHTML DOM) or is missing `constructor` altogether (e.g. if
> it was overwritten). I remember seeing solutions involving deleting
> object's `__proto__` (if supported), checking property with `in` and
> then restoring `__proto__` back. Relying on such manipulations is
> like playing with fire, of course : ) It is probably also slower.
Yep, sounds dangerous!
--
Jim
my wiki ajaxification thing: http://wikizzle.org
my blog: http://jimhigson.blogspot.com/
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