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Truly hidden object property?

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  Truly hidden object property? JJ <jaejunks@glegooilma-swapit.com> - 2012-12-02 16:57 +0000

#17410 — Truly hidden object property?

When opening an RSS URL using Opera web browser, Opera will preview it 
like a web page. Opera processes the RSS and store the RSS data in 
"opera.feed". The interesting thing is that the "feed" property, even 
though it's enumerable, it's not included in "Object.getOwnPropertyNames
(opera)" result. Here's some code to show what I meant (on previewed 
RSS).

var a=Object.getOwnPropertyNames(opera);
console.log(a.join('\n'));
/* result:
renderingMode
stpVersion
buildNumber
version
collect
postError
getLocaleString
addEventListener
removeEventListener
defineMagicFunction
defineMagicVariable
getOverrideHistoryNavigationMode
setOverrideHistoryNavigationMode
getPreference
getPreferenceDefault
setPreference
FeedEntry
Feed
deleteDatabase
*/
//note: opera.Feed !== opera.feed
//opera.Feed is a constructor, and opera.feed is an object

var a=Object.getOwnPropertyDescriptor(opera,'feed');
console.log(JSON.stringify(a));
//result: {"enumerable":true,"configurable":true}
//note: descriptor's "get" and "set" are Opera native functions

//"feed" property isn't an inherited property,
//since it's a direct descendant of Object.
console.log(opera.__proto__ === Object.prototype);
//result: true


"Object.getOwnPropertyNames" should list all properties, whether they're 
enumerable or not.

Any property created using "Object.__defineGetter__" should also be 
included in "Object.getOwnPropertyNames" result.

I thought it was done using "opera.defineMagicVariable", but it can't 
create a variable as a property of other object. For example:

//this is ok
opera.defineMagicVariable('abc',
  function(){ //getter
    return 123;
  },
  function(){ //setter
  }
);
console.log(typeof abc); //number
//this is not ok
var abc={};
opera.defineMagicVariable('abc.def',
  function(){ //getter
    return 123;
  },
  function(){ //setter
  }
);
console.log(typeof abc); //object
console.log(typeof abc.def); //undefined


The "call" and "apply" can't also be used on "opera.defineMagicVariable" 
since its "this" must be global context like "setTimeout".

How is this truly hidden property possible?
Is it one of Opera magic?

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