when copy node js custom error class super Error variable is gone - node.js

Question

I have a custom Err class that extends from Error class. all thing was good until I copy an instance of Err class. the super's variables of copied instance are undefined!
here is my code:
class Err extends Error {
constructor(code, msg) {
super(msg);
this.code = code;
}
}
const error = new Err(404, 'error message');
console.log(error);
/* { Error: error message
at repl:1:15
at Script.runInThisContext (vm.js:122:20)
at REPLServer.defaultEval (repl.js:332:29)
at bound (domain.js:402:14)
at REPLServer.runBound [as eval] (domain.js:415:12)
at REPLServer.onLine (repl.js:642:10)
at REPLServer.emit (events.js:203:15)
at REPLServer.EventEmitter.emit (domain.js:448:20)
at REPLServer.Interface._onLine (readline.js:308:10)
at REPLServer.Interface._line (readline.js:656:8) code: 404 }
*/
const copy = { ...error };
console.log(copy);
// { code: 404 }
// where is error.stack and error.name?
SOLUTION:
Change copy method to this
const copy= { ...error };
copy.name = error.name;
copy.message = error.message;
copy.stack = error.stack;
tanks PA.
if any one has a better solution tell it to me.

Answer 1

with copy = { ...error };
(1) the {} object literal operator, creates a new Object, not a new Err object,
and
(2) the ... or spread properties operator, for object literals, just copies the provided object own enumerable properties onto your new object.
To clone any javascript class instance with a perfect copy of properties, methods, getters/setters, non-enumerable properties, etc, ina a generic code is almost impossible. You may create your own copy/clone code for your particular case, with a combination of Object.assign() / Object.getPrototype() and custom tuning for inherited properties and internal classes.