webView.evaluateJavaScript("document.documentElement.outerHTML.toString()",completionHandler: { (html: Any?,error: Error?) in
    print(html)
})

您还可以注入一些返回HTML的JavaScript.

let script = WKUserScript(source: javascriptString,injectionTime: injectionTime,forMainFrameOnly: true)
userContentController.addUserScript(script)
self.webView.configuration.userContentController.addScriptMessageHandler(self,name: "didGetHTML")

…

func userContentController(userContentController: WKUserContentController,didReceiveScriptMessage message: WKScriptMessage) {

        if message.name == "didGetHTML" {
            if let html = message.body as? String {
                print(html)
            }
        }
}

你可以注入的javascript看起来像：

webkit.messageHandlers.didGetHTML.postMessage(document.documentElement.outerHTML.toString());