Sending Data from WebView To React Native

index.js

//This sends data from WebView to React Native
...
<script>
  window.postMessage("Sending data from WebView");
</script>
...


//In order to get data the was sent from WebView use onMessage prop on <WebView>
...
<WebView
   ref="webview"
    onMessage={this.onMessage}
/>
  
onMessage(data) {
  //Prints out data that was passed.
  console.log(data);
}
....