observable-ref

class MyStore {
  @observable.ref deviceStatus; // Device status is sth. like { isConnected, etc. }
  
  @action
  updateStatus = (deviceStatus) => {
    this.deviceStatus = deviceStatus;
  }
};

const store = new MyStore();

const websocket = new WebSocket(...);
websocket.onmessage = function (event) {
  store.updateStatus(JSON.parse(event.data));
}