In the answer of the question 19 you wrote: "By default enumerable is true when creating object.". However the default may be 'false'. Please check it again.
reference:
[https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperties#enumerable]
[enumerable]
true if and only if this property shows up during enumeration of the properties on the corresponding object. Defaults to false.
In the answer of the question 19 you wrote: "By default enumerable is true when creating object.". However the default may be 'false'. Please check it again.
reference:
[https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperties#enumerable]
[enumerable]
true if and only if this property shows up during enumeration of the properties on the corresponding object. Defaults to false.