Embed JavaScript code in Webview iOS

Question

I created an iOS web browser with a fast language code. And add an extra button to enter the script on this web page, but it always crashes when you try:

webView!.evaluateJavaScript("document.body.style.background = 'red';", nil) 

Any idea how to fix this? And how to read JavaScript code from a file, and then enter it into this web viewer.

I use a code style like this example, but with WKWebView: https://github.com/rshankras/WebViewDemo

If you can solve this question, I need the basic working code in the answer. And a solution for loading JavaScript from a file. And add this code to the WKWebView element.

Answer 1

I do not see the method that you use (evaluate JavaScript) in the current UIWebView API Documents , but it is in the WKWebView Documents . Maybe you are using the wrong API? Maybe try using stringByEvaluatingJavaScriptFromString (_ :) instead:

 let script = "document.body.style.background = 'red'" if let result = webView.stringByEvaluatingJavaScriptFromString(script) { println("result is \(result)") } 

Also, I'm not sure that "!" (prediction tells me this is wrong), since there is no context around your code. So maybe try both versions.

Getting a line from a file looks something like this:

 let path = NSBundle.mainBundle().pathForResource("jsFileName", ofType: "js") if let content = String.stringWithContentsOfFile(path, encoding: NSUTF8StringEncoding, error: nil) { println("js content is \(content)") } 

Booting from disk has many variables around how your file is copied and stored, so you will have to do some work to match the path variable in your structure.

Answer 2

This will work with WKWebView. Remember to add the WebKit framework on top of your class definition

  var webView: WKWebView! func loadWebViewWithCustomJavaScript { //Create Preferences let preferences = WKPreferences() preferences.javaScriptEnabled = true //Initialise javascript file with user content controller and configuration let configuration = WKWebViewConfiguration() let scriptURL = NSBundle.mainBundle().pathForResource("Your File Name", ofType: "js") var scriptContent = "" do { scriptContent = try String(contentsOfFile: scriptURL!, encoding: NSUTF8StringEncoding) } catch{ print("Cannot Load File") } let script = WKUserScript(source: scriptContent, injectionTime: .AtDocumentStart, forMainFrameOnly: true) configuration.userContentController.addUserScript(script) configuration.preferences = preferences //Create WebView instance webView = WKWebView(frame: CGRectMake(0,0, self.view.frame.size.width, self.view.frame.size.height), configuration: configuration) view.addSubview(webView) //Finally load the url let url = NSURL(string:"your URL") let urlRequest = NSURLRequest(URL: url!) webView.loadRequest(urlRequest) } 

Sample JavaScript Injection Code

  //Hides name of "background1" element on the page var styleTag = document.createElement("style"); styleTag.textContent = 'div#background1, .after-post.widget-area {display:none;}'; document.documentElement.appendChild(styleTag); 

Answer 3

Got a job using the following. Used String instead of NSString to use native swift 2. Javascript code for injection should be in the hidesections.js file

  let jsPath = NSBundle.mainBundle().pathForResource("hidesections", ofType: "js"); let jsContent: String? do { jsContent = try String(contentsOfFile: jsPath!, encoding: NSUTF8StringEncoding) } catch _ { jsContent = nil } webView.stringByEvaluatingJavaScriptFromString(jsContent!) 

Answer 4

If you are using WKWebView , here is the solution.

 if let scriptFile = NSBundle.mainBundle().pathForResource("script", ofType: "js") { var error: NSError? let scriptString = NSString(contentsOfFile: scriptFile, encoding: NSUTF8StringEncoding, error: &error) if let error = error { println("Error: Could not load script file => \(error)") } else { if let scriptString = scriptString { let script = WKUserScript(source: scriptString, injectionTime: .AtDocumentEnd, forMainFrameOnly: true) let controller = WKUserContentController() controller.addUserScript(script) let configuration = WKWebViewConfiguration() configuration.userContentController = controller let webView = WKWebView(frame: self.view.bounds, configuration: configuration) self.webView = webView self.view.addSubview(webView) } } }