liveData.js

class BeerList extends React.Component {

  componentDidMount() {
    this.changeListener =
        DeviceEventEmitter.addListener(
          'beersChanged',
          this.onBeersChanged);
    NativeModules.BeerLiveData.subscribe();
  }

  componentWillUnmount() {
    this.changeListener.remove();
    NativeModules.BeerLiveData.unsubscribe();
  }

  beersChanged = (event) => {
    const beers = JSON.parse(event.beers);
    this.setState({beers: beers});
  }

  // ...

}