     }
 }
 
-extension ViewController : WKScriptMessageHandler {
+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;

        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: WKNavigationDelegate {
    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        print("didFinish navigation:")
    }
}
