In Swift, it is possible to inject a JavaScript code into a WKWebView and execute it from your app. The below code example demonstrates how to:
- Load HTML file from a local file,
- Load JavaScript code from a local file,
- Create WKUserScript object,
- Inject JavaScript into an HTML document.
Load HTML File From App Bundle
let myProjectBundle:Bundle = Bundle.main
let myUrl = myProjectBundle.url(forResource: "my-html-file", withExtension: "html")!
myWebView.loadFileURL(myUrl,allowingReadAccessTo: myUrl)
Load JavaScript Code From a Local File
The below code example is a function which you can add to your Swift file and call to load the content of a demo-script.js file.
func getMyJavaScript() -> String {
if let filepath = Bundle.main.path(forResource: "demo-script", ofType: "js") {
return try String(contentsOfFile: filepath)
where:
demo-script – is the name of a file. Notice that there is no need to specify file extension here.
js – The demo-script file extension.
Inject JavaScript to WKWebView with WKUserScript
var myWebView: WKWebView!
override func viewDidLoad() {
let config = WKWebViewConfiguration()
let js = getMyJavaScript()
let script = WKUserScript(source: js, injectionTime: .atDocumentEnd, forMainFrameOnly: false)
config.userContentController.addUserScript(script)
config.userContentController.add(self, name: "clickListener")
myWebView = WKWebView(frame: view.bounds, configuration: config)
myWebView.uiDelegate = self
myWebView.navigationDelegate = self
view.addSubview(myWebView!)
where:
getMyJavaScript() – is a function that loads JavaScript from a local file. The source code of this function is also on this page.
Complete Example
class MyWebViewViewController: UIViewController, WKNavigationDelegate, WKUIDelegate, WKScriptMessageHandler {
var myWebView: WKWebView!
override func viewDidLoad() {
let config = WKWebViewConfiguration()
let js = getMyJavaScript()
let script = WKUserScript(source: js, injectionTime: .atDocumentEnd, forMainFrameOnly: false)
config.userContentController.addUserScript(script)
config.userContentController.add(self, name: "clickListener")
myWebView = WKWebView(frame: view.bounds, configuration: config)
myWebView.uiDelegate = self
myWebView.navigationDelegate = self
view.addSubview(myWebView!)
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
let myProjectBundle:Bundle = Bundle.main
let myUrl = myProjectBundle.url(forResource: "my-html-file", withExtension: "html")!
myWebView.loadFileURL(myUrl,allowingReadAccessTo: myUrl)
//let url = URL(string: "https://appsdeveloperblog.com")!
//myWebView.load(URLRequest(url: url))
func getMyJavaScript() -> String {
if let filepath = Bundle.main.path(forResource: "demo-script", ofType: "js") {
return try String(contentsOfFile: filepath)
func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
For more Swift code examples and tutorials, please check the Swift Code Examples page on this website.
