JS调用WKWebView弹窗

WKWebView自带禁止弹窗显示，通过js alert不可以调用系统弹窗，所以需要额外增加两个代理实现js弹窗。

 // 监听通过JS调用警告框
    func webView(_ webView: WKWebView, runJavaScriptAlertPanelWithMessage message: String, initiatedByFrame frame: WKFrameInfo, completionHandler: @escaping () -> Void) {
        let alert = UIAlertController(title: nil, message: message, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "确定", style: .default, handler: { (action) in
            completionHandler()
        }))
        self.present(alert, animated: true, completion: nil)
    }

    // 监听通过JS调用提示框
    func webView(_ webView: WKWebView, runJavaScriptConfirmPanelWithMessage message: String, initiatedByFrame frame: WKFrameInfo, completionHandler: @escaping (Bool) -> Void) {
        let alert = UIAlertController(title: nil, message: message, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "确定", style: .default, handler: { (action) in
            completionHandler(true)
        }))
        alert.addAction(UIAlertAction(title: "取消", style: .default, handler: { (action) in
            completionHandler(false)
        }))
        self.present(alert, animated: true, completion: nil)
    }
    
    // 监听JS调用输入框
    func webView(_ webView: WKWebView, runJavaScriptTextInputPanelWithPrompt prompt: String, defaultText: String?, initiatedByFrame frame: WKFrameInfo, completionHandler: @escaping (String?) -> Void) {
        // 类似上面两个方法
    }