const values = JSON.parse('[3,5]');
values.extra = 7;
Object.defineProperty(values, 'hidden', { value: 9, writable: true, configurable: true });
console.log(values.extra, values.hidden, values.length);
console.log(Object.keys(values).join(','));
console.log(Object.getOwnPropertyNames(values).join(','));
console.log(Object.hasOwn(values, 'extra'), 'hidden' in values);
console.log(Object.getOwnPropertyDescriptor(values, 'hidden').enumerable);
console.log(Object.getOwnPropertyDescriptors(values).extra.value);
const keys = [];
for (const key in values) keys.push(key);
console.log(keys.join(','));
delete values.hidden;
console.log(Object.hasOwn(values, 'hidden'));
Object.seal(values);
console.log(Object.isSealed(values), Object.isFrozen(values));
console.log(Object.getOwnPropertyDescriptor(values, 'extra').configurable);
values.extra = 8;
console.log(values.extra);
Object.freeze(values);
console.log(Object.isFrozen(values), Object.getOwnPropertyDescriptor(values, 'extra').writable);