 
 // Wrap the WKWebView webview to allow IB use
 
-class MyWebView : WKWebView {
+class MyWebView: WKWebView {
     required init?(coder: NSCoder) {
         let configuration = WKWebViewConfiguration()
         let controller = WKUserContentController()
-        configuration.userContentController = controller;
+        configuration.userContentController = controller
         super.init(frame: CGRect.zero, configuration: configuration)
     }
 }

        super.viewDidLoad()

        title = "WKWebView"
        webView.navigationDelegate = self;

        // Add addScriptMessageHandler in javascript: window.webkit.messageHandlers.MyObserver.postMessage()
        webView.configuration.userContentController.add(self, name: "MyObserver")

    }
}

extension ViewController: WKScriptMessageHandler {
    func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
        // Callback from javascript: window.webkit.messageHandlers.MyObserver.postMessage(message)
        let text = message.body as! String;
