code: function handleMessage(event) {
    if (!event.data) {
      return;
    }
  
    switch (event.data) {
      case 'NETWORK_IDLE_ENQUIRY_RESULT_IDLE':
      case 'NETWORK_IDLE_CALLBACK':
        networkIdleCallback.__callbacks__.forEach(callback => {
          networkIdleCallback.__popCallback__(callback, false);
        });
        break;
    }
  }
docs: Handle message passing
  @param {*} event - A valid event