funkydevil/index.html

## index.html
<!DOCTYPE HTML>
<html>
    <head>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <style>
    .block {
      display: block;
      width: 100%;
      border: none;
      background-color: #04AA6D;
      color: white;
      padding: 14px 28px;
      font-size: 16px;
      cursor: pointer;
      text-align: center;
    }

    .block:hover {
      background-color: #ddd;
      color: black;
    }
    </style>
    </head>

<body>
  <button onclick="showAlert()" class="block">Show alert</button>
  <button onclick="createTextField()" class="block">createTextField</button>
  <button onclick="swiftFunction()" class="block">call swiftFunction</button>
  <button onclick="injectedFunction()" class="block">call injectedFunction</button>

  <script>
	  function showAlert() {
	      alert( 'hello world!' );
	  }

	  function createTextField() {
	    var x = document.createElement("INPUT");
	    x.setAttribute("type", "text");
	    x.setAttribute("value", "Hello World!");
	    document.body.appendChild(x);
	  }

	  function getValueFromJS() {
	  	return "hello";
	  }

	  function swiftFunction() {
	  	window.webkit.messageHandlers.testFunc.postMessage({param1: "111", param2: "222"});
	  }
  </script>
</body>

</html>

## viewController.swift
//
//  ViewController.swift
//  JSCallExample
//
//  Created by Kirill Pyulzyu on 15.02.2022.
//

import UIKit
import WebKit

class ViewController: UIViewController {
    var webview: WKWebView!
    let jsHandler = "testFunc"

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.

        addWKWebView()

        loadHTML()
    }


    func addWKWebView() {
        let width = self.view.frame.width
        let height = self.view.frame.height
        let webviewFrame = CGRect(x: 0, y: height/2, width: width, height: height/2)


        let contentController = WKUserContentController()
        let scriptSource = "function injectedFunction() { alert('testtest') }"
        let script = WKUserScript(source: scriptSource, injectionTime: .atDocumentEnd, forMainFrameOnly: true)
        contentController.addUserScript(script)

        let configuration = WKWebViewConfiguration()
        configuration.userContentController = contentController
        configuration.userContentController.add(self, name: jsHandler)

        webview = WKWebView(frame: webviewFrame, configuration: configuration)
        webview.uiDelegate = self
        view.addSubview(webview)
    }

    func loadHTML() {
        guard let webview = webview else {
            return
        }
        let url = Bundle.main.url(forResource: "index.html", withExtension: nil)!
        webview.loadFileURL(url, allowingReadAccessTo: url)
    }

    @IBAction func onCallJSTapped(_ sender: Any) {
        webview?.evaluateJavaScript("createTextField()", completionHandler: { result, error in
        })
    }

    @IBAction func getValueFromJS(_ sender: Any) {
        webview?.evaluateJavaScript("getValueFromJS()", completionHandler: { result, error in
            print(result!)
        })
    }

}

extension ViewController: WKScriptMessageHandler {
    func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
        if message.name == jsHandler {
            guard let params = message.body as? [String: String] else {
                return
            }

            for (key, value) in params {
                print(key + " = " + value)
            }
        }
    }

}


extension ViewController: WKUIDelegate {

    func webView(_ webView: WKWebView, runJavaScriptAlertPanelWithMessage message: String, initiatedByFrame frame: WKFrameInfo,
                 completionHandler: @escaping () -> Void) {

        let alertController = UIAlertController(title: nil, message: message, preferredStyle: .actionSheet)
        alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action) in
            completionHandler()
        }))

        present(alertController, animated: true, completion: nil)
    }


    func webView(_ webView: WKWebView, runJavaScriptConfirmPanelWithMessage message: String, initiatedByFrame frame: WKFrameInfo,
                 completionHandler: @escaping (Bool) -> Void) {

        let alertController = UIAlertController(title: nil, message: message, preferredStyle: .actionSheet)

        alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action) in
            completionHandler(true)
        }))

        alertController.addAction(UIAlertAction(title: "Cancel", style: .default, handler: { (action) in
            completionHandler(false)
        }))

        present(alertController, animated: true, completion: nil)
    }


    func webView(_ webView: WKWebView, runJavaScriptTextInputPanelWithPrompt prompt: String, defaultText: String?, initiatedByFrame frame: WKFrameInfo,
                 completionHandler: @escaping (String?) -> Void) {

        let alertController = UIAlertController(title: nil, message: prompt, preferredStyle: .actionSheet)

        alertController.addTextField { (textField) in
            textField.text = defaultText
        }

        alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action) in
            if let text = alertController.textFields?.first?.text {
                completionHandler(text)
            } else {
                completionHandler(defaultText)
            }
        }))

        alertController.addAction(UIAlertAction(title: "Cancel", style: .default, handler: { (action) in
            completionHandler(nil)
        }))

        present(alertController, animated: true, completion: nil)
    }
}
	<!DOCTYPE HTML>
	<html>
	<head>
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<style>
	.block {
	display: block;
	width: 100%;
	border: none;
	background-color: #04AA6D;
	color: white;
	padding: 14px 28px;
	font-size: 16px;
	cursor: pointer;
	text-align: center;
	}

	.block:hover {
	background-color: #ddd;
	color: black;
	}
	</style>
	</head>

	<body>
	<button onclick="showAlert()" class="block">Show alert</button>
	<button onclick="createTextField()" class="block">createTextField</button>
	<button onclick="swiftFunction()" class="block">call swiftFunction</button>
	<button onclick="injectedFunction()" class="block">call injectedFunction</button>

	<script>
	function showAlert() {
	alert( 'hello world!' );
	}

	function createTextField() {
	var x = document.createElement("INPUT");
	x.setAttribute("type", "text");
	x.setAttribute("value", "Hello World!");
	document.body.appendChild(x);
	}

	function getValueFromJS() {
	return "hello";
	}

	function swiftFunction() {
	window.webkit.messageHandlers.testFunc.postMessage({param1: "111", param2: "222"});
	}
	</script>
	</body>

	</html>
	//
	// ViewController.swift
	// JSCallExample
	//
	// Created by Kirill Pyulzyu on 15.02.2022.
	//

	import UIKit
	import WebKit

	class ViewController: UIViewController {
	var webview: WKWebView!
	let jsHandler = "testFunc"

	override func viewDidLoad() {
	super.viewDidLoad()
	// Do any additional setup after loading the view.

	addWKWebView()

	loadHTML()
	}


	func addWKWebView() {
	let width = self.view.frame.width
	let height = self.view.frame.height
	let webviewFrame = CGRect(x: 0, y: height/2, width: width, height: height/2)


	let contentController = WKUserContentController()
	let scriptSource = "function injectedFunction() { alert('testtest') }"
	let script = WKUserScript(source: scriptSource, injectionTime: .atDocumentEnd, forMainFrameOnly: true)
	contentController.addUserScript(script)

	let configuration = WKWebViewConfiguration()
	configuration.userContentController = contentController
	configuration.userContentController.add(self, name: jsHandler)

	webview = WKWebView(frame: webviewFrame, configuration: configuration)
	webview.uiDelegate = self
	view.addSubview(webview)
	}

	func loadHTML() {
	guard let webview = webview else {
	return
	}
	let url = Bundle.main.url(forResource: "index.html", withExtension: nil)!
	webview.loadFileURL(url, allowingReadAccessTo: url)
	}

	@IBAction func onCallJSTapped(_ sender: Any) {
	webview?.evaluateJavaScript("createTextField()", completionHandler: { result, error in
	})
	}

	@IBAction func getValueFromJS(_ sender: Any) {
	webview?.evaluateJavaScript("getValueFromJS()", completionHandler: { result, error in
	print(result!)
	})
	}

	}

	extension ViewController: WKScriptMessageHandler {
	func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
	if message.name == jsHandler {
	guard let params = message.body as? [String: String] else {
	return
	}

	for (key, value) in params {
	print(key + " = " + value)
	}
	}
	}

	}


	extension ViewController: WKUIDelegate {

	func webView(_ webView: WKWebView, runJavaScriptAlertPanelWithMessage message: String, initiatedByFrame frame: WKFrameInfo,
	completionHandler: @escaping () -> Void) {

	let alertController = UIAlertController(title: nil, message: message, preferredStyle: .actionSheet)
	alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action) in
	completionHandler()
	}))

	present(alertController, animated: true, completion: nil)
	}


	func webView(_ webView: WKWebView, runJavaScriptConfirmPanelWithMessage message: String, initiatedByFrame frame: WKFrameInfo,
	completionHandler: @escaping (Bool) -> Void) {

	let alertController = UIAlertController(title: nil, message: message, preferredStyle: .actionSheet)

	alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action) in
	completionHandler(true)
	}))

	alertController.addAction(UIAlertAction(title: "Cancel", style: .default, handler: { (action) in
	completionHandler(false)
	}))

	present(alertController, animated: true, completion: nil)
	}


	func webView(_ webView: WKWebView, runJavaScriptTextInputPanelWithPrompt prompt: String, defaultText: String?, initiatedByFrame frame: WKFrameInfo,
	completionHandler: @escaping (String?) -> Void) {

	let alertController = UIAlertController(title: nil, message: prompt, preferredStyle: .actionSheet)

	alertController.addTextField { (textField) in
	textField.text = defaultText
	}

	alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action) in
	if let text = alertController.textFields?.first?.text {
	completionHandler(text)
	} else {
	completionHandler(defaultText)
	}
	}))

	alertController.addAction(UIAlertAction(title: "Cancel", style: .default, handler: { (action) in
	completionHandler(nil)
	}))

	present(alertController, animated: true, completion: nil)
	}
	}