Javascript in WKWebView - evaluateJavaScript vs addUserScript

Question

I am trying to understand the best way to execute javascript with WKWebview

Could someone please give me the use cases / best practices when using WKWebView.

When to use addUserScript and WKScriptMessageHandler and when to use evaluateJavaScript

    let jscript = "my script"
    let userScript = WKUserScript(source: jscript, injectionTime: .atDocumentEnd, forMainFrameOnly: true)
    let userContentController = WKUserContentController()
    userContentController.addUserScript(userScript)

    let webViewConfiguration = WKWebViewConfiguration()
    webViewConfiguration.userContentController = userContentController
    webView = WKWebView(frame: self.view.bounds, configuration: webViewConfiguration)

vs

let myScript
self.wkWebView.evaluateJavaScript(script) { (result, error) in
    if error != nil {
        print("\(error)")
    }
}

Answer 1

Found a nice explanation

http://jonathanblog2000.blogspot.co.il/2016/11/understanding-ios-wkwebview.html

2.3.2 Inject javascript from native code to js DOM emphasized text WKUserContentController allows add (and remove) a WKUserScript to be injected either when the DOM tree starts to load or finishes to load. On the contrary, evaluateJavaScript allows application to execute a javascript snippet on demand at any time.

Answer 2

In my experience, WKUserScript seems to have more privileges, eg: document.cookie="test=test" works with WKUserScript but not with evaluateJavaScript.

However, WKUserScript requires an additional reload() for the javascript you injected to run. It maybe a bug. Sometimes it complicates the code.

WKScriptMessageHandler is a separate thing. It allows your native app to receive messages from javascript. eg, you can add a handler and receives message that is posted from javascript like: "window.webkit.messageHandlers.notification.postMessage({body: "..."});" Refer: http://nshipster.com/wkwebkit/

Pretty cool stuff that doesn't exist in UIWebView