jQuery.isPlainObject() always returns false when Object.prototype has a properties

[[email protected]…]

jQuery.isPlainObject() finally enumerates all propertyes of an object. If the last property is own, then function relies that it is an Object. As the result, it is not allowed to have any properties in prototype. So, if we extend Object.prototype with at least one property, jQuery.isPlainObject() will always return false for new objects, created after.

jsFiddle: ​http://jsfiddle.net/kqe95/

alert(jQuery.isPlainObject({})); // true
Object.prototype.foo = function(){};
alert(jQuery.isPlainObject({})); // false

[Rick Waldron]

​http://docs.jquery.com/Won't_Fix

[[email protected]…]

This is still not fixed! Besides the function does a lot of "stuff" and its performance is very low! It is extensively used by $.extend when creating deep copies!

Why not simply comparing either object.proto == Object.prototype or in IE Object.getPrototypeOf(object) == Object.prototype

if Object.getPrototypeOf is missing as well, the current implementation could be good enough

Tests are here: ​http://jsfiddle.net/LLKET/1/

[Rick Waldron]

Right... it's not fixed because I closed it as "won't fix", because jQuery won't fix bugs that are caused by user code that does stupid things like extending Object.prototype

[vovan-ve]

Replying to rwaldron:

... user code that does stupid things like extending Object.prototype

I still think, that You are not right. Can you give a prooflink to confirm this words?

[[email protected]…]

Why my above approach is not a good fix for all modern browsers?

[vovan-ve]

Replying to [email protected]…:

Why my above approach is not a good fix for all modern browsers?

1. ​http://jsfiddle.net/FdSwc/

   function Foo() {};
   Foo.prototype = Object.prototype;
   alert( new Foo().__proto__ === Object.prototype );
   

2. one_window.Object !== another_window.Object;

   /* this is window A */
   window.FooBar = {};
   open('<url to run next code in B>');
   
   /* this is window B opened by window.open() in A */
   alert( opener.Object === Object ); // false
   alert( opener.FooBar.__proto__ === Object.prototype ); // false
   alert( opener.FooBar.__proto__ === opener.Object.prototype ); // true
   

[[email protected]…]

That's correct but I think you really don't care about that. It may be useful in 0.001% of cases, whereas you could use the current option.

[Rick Waldron]

Replying to vovan-ve:

Replying to rwaldron:

... user code that does stupid things like extending Object.prototype

I still think, that You are not right. Can you give a prooflink to confirm this words?

jQuery's Won't Fix: ​http://contribute.jquery.org/wont-fix/

The problem with adding properties to Object.prototype is that all Object's will then inherit those properties, whether they want to or not—and these properties will appear in for-in loops.

Since ES5, Object.prototype can be safely augmented with Object.definePropert(y|ies) by creating a properties and specifying that its enumerable? field is false.

• "Object.prototype is verboten" ​http://erik.eae.net/archives/2005/06/06/22.13.54/
• "Deep-extending objects in JavaScript" ​http://andrewdupont.net/2009/08/28/deep-extending-objects-in-javascript/
• "Extending JavaScript Natives" ​http://javascriptweblog.wordpress.com/2011/12/05/extending-javascript-natives/
• "Extending built-in native objects. Evil or not?" ​http://perfectionkills.com/extending-built-in-native-objects-evil-or-not/

[anonymous]

Replying to rwaldron:

Replying to vovan-ve:

• "Object.prototype is verboten" ​http://erik.eae.net/archives/2005/06/06/22.13.54/

...

Thanks for the links. Now I see I'm not right.

[DotNetWise]

Even so, jQuery will simply fail when Object.prototype will have something added. But that can be sorted out with ES5 Object.defineProperty("someProperty", { enumerable: false});