Comunicar una Web en React con un Frame dentro de React o web HTML con JavaScript usando postMessage()

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Tiempo de lectura: 2 minutos

Today we’re going to see how we can communicate a web created with React with an iFrame or frame in React or HTML with JavaScript.

Loading the Frame

We create an iframe:

<iframe
     src={urlCargar}
     style={{ width: '100%', height: '500px' }}
     />

In urlCargar we put the URL of the web from which we want to capture the event.

Now we create the event that will allow us to obtain the data:

  useEffect(() => {
        function handleReceiveMessage(event: MessageEvent) {
            // Check if the origin of the message is the expected one
            if (event.origin !== "http://localhost:3000" && event.origin !== "your_url") {
                // Do not handle the message if the origin is unknown
                return;
            }

            // If it's not JSON (we receive plain text):
            // alert(receivedData);

           // If a JSON object is received:
           const receivedData = JSON.parse(event.data);
           alert(JSON.stringify(receivedData));
        }

        window.addEventListener('message', handleReceiveMessage);

        return () => {
            window.removeEventListener('message', handleReceiveMessage);
        };
    }, []);

First we check that we are receiving from the correct URL:

            if (event.origin !== "http://localhost:3000" && event.origin !== "your_url") {
                // Do not handle the message if the origin is unknown
                return;
            }

*You must indicate in your_url the URL where you expect to receive the events.

And now, to obtain the event, if it is text or an object it is done as follows:

            // If it's not JSON (we receive plain text):
            // alert(receivedData);

           // If a JSON object is received:
           const receivedData = JSON.parse(event.data);
           alert(JSON.stringify(receivedData));

React

In React we are going to create a web for example test.tsx

First we have to define a new type for Window (which React Native WebView asks us for)

declare global {
  interface Window { 
    ReactNativeWebView: any; 
  }
}

And now simply where we want to communicate the event we can:

window.ReactNativeWebView.postMessage("Hello");

Or we can even send JSON objects:

window.parent.postMessage(JSON.stringify(objToSend));
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