UIWebView delegate method shouldStartLoadWithRequest: equivalent in WKWebView?

Question

I have a module inside my iOS 7+ app which is a UIWebView. The html page loads a javascript that creates custom-shaped buttons (using the Raphaeljs library). With UIWebView,

Answer 1

for swift 4.2: (taking from Yifei He 何一非. )

 func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: (WKNavigationActionPolicy) -> Void) {

        let url = navigationAction.request.url
        let urlStr = url?.absoluteString
        switch urlStr {
        case BASE_URL:
            //self.someFunc()
            decisionHandler(.cancel)
            break
        default:
            decisionHandler(.allow)
            break
        }

    }