how to use javascript channel in flutter web webview?

Question

controller = WebViewController()
      ..setJavaScriptMode(JavaScriptMode.unrestricted)
      ..setBackgroundColor(Color.fromARGB(255, 255, 255, 255))
      ..addJavaScriptChannel('app', onMessageReceived: (s) {
        if (s.message == "close") {..}

how to add javascript channel like this in the web version of flutter webview?

are there any plugins where i can establish a jsChannel or write a function for the same?