document.hasOwnProperty（“ hidden”）返回false，但是文档具有隐藏的属性

Question

I'm trying to check if document has 'hidden' property using document.hasOwnProperty but it always returns false in Chrome (74).

I've tried Object.prototype.hasOwnProperty but that too returns false. When I tried to stringify and parse back document I got back Location object as a property.

 console.log(document.hasOwnProperty("hidden")); console.log(Object.prototype.hasOwnProperty.call(document, "false")); console.log(JSON.parse(JSON.stringify(document))); console.log(typeof document.hidden !== "undefined"); console.log(document.hidden); console.log(Document.prototype.hasOwnProperty.call(document, "hidden")); console.log(Document.prototype.hasOwnProperty.call(document, "location")); 

Shouldn't hasOwnProperty check if an object has a property irrespective of the object type? I apologize if the question has already been answered.

Answer 1

The purpose of hasOwnProperty() is to check whether a certain property is defined on the instance itself and is not inherited through its prototype .

In the case of document , it rightfully returns false since the hidden property is actually defined on the Document interface and not on the instance itself.

(thanks to @Jonas Wilms for clarification)

Answer 2

Copying and correcting @haim770's deleted answer for now:

The purpose of hasOwnProperty() is to check whether a certain property is defined on the object itself and is not inherited through its prototype .

In the case of document , it rightfully returns false since the hidden property is actually defined on [ Document ] and not on [the document object] itself.

 console.log('' + Object.getPrototypeOf(document)); console.log('' + Object.getPrototypeOf(Object.getPrototypeOf(document))); console.log(document.__proto__.__proto__.hasOwnProperty('hidden')); console.log(Object.getOwnPropertyDescriptor(Document.prototype, 'hidden'));