[removed] find the prototype object to which a property belongs

Question

I have an instance from Square which inherits from Rectangle

instance instanceof Rectangle --> true
instance instanceof Square    --> true
instance.are         


        

Answer 1

No. There isn't. You have to traverse the prototype chain:

function owner(obj, prop) {
    var hasOwnProperty = Object.prototype.hasOwnProperty;
    while (obj && !hasOwnProperty.call(obj, prop))
        obj = Object.getPrototypeOf(obj);
    return obj;
}

Now you simply do:

var obj = owner(instance, "area");
console.log(obj === Rectangle);    // true

If instance or its prototypes do not have the property area then owner returns null.