onmessage = (e) => {
  const data = JSON.stringify(e.data.editorState, getCircularReplacer(), e.data.spaces);
  postMessage(data);
};

const getCircularReplacer = () => {
  return (key, value) => {
    if (key === 'containers') {
      return [...value.entries()]
        .map(([Key, Value]) => ({ Key, Value }));
    }

    if (key === 'symbols') {
      return [...value.entries()]
        .map(([Key, Value]) => ({ Key, Value }));
    }

    if (key === 'linkedContainers') {
      return Array.from(value);
    }

    return value;
  };
};