This is how you perform a deep copy in javascript as discussed in the HN article: Deep-copying in JavaScript.

deep_copy.js

function deepCopy(obj) {
  return new Promise(resolve => {
    const {send, recv} = new MessageChannel();
    recv.onmessage = ev => resolve(ev.data);
    send.postMessage(obj);
  });
}

const obj = /* object to copy */;
const clone = await deepCopy(obj);