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javascriptobjectdomhasownproperty

document.hasOwnProperty("hidden") returns false but document has the property hidden

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.

Solution

  • 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)