Add event listener from iOS code and then get callback in native code

WKWebViewEventListener.swift

    func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
        print("\(#function): \(message)")
    }
    
    func setupSubViews() {
        let configurations = WKWebViewConfiguration()
        let controller = WKUserContentController()
        let myEventScriptString =
        """
        var elements = document.getElementsByClassName('button');
        for (var i = 0 ; i < elements.length; i++) {
            elements[i].addEventListener('click', function() {
                window.webkit.messageHandlers.myEvent.postMessage(JSON.stringify(true));
            });
        }
        """
        let myEventScript = WKUserScript(source: myEventScriptString, injectionTime: .atDocumentEnd, forMainFrameOnly: false)
        controller.addUserScript(myEventScript)
        controller.add(self, name: "myEvent")
        configurations.userContentController = controller
        configurations.allowsInlineMediaPlayback = true
        webView = WKWebView(frame: .zero, configuration: configurations)
        // Layout.add(webView, in: view!)
        webView.navigationDelegate = self
    }