swift调用网页中的点击事情

swift代码

func webViewDidFinishLoad(_ webView: UIWebView) {
    let context = webView.value(forKeyPath: "documentView.webView.mainFrame.javaScriptContext") as? JSContext
    let callBack : @convention(block) (AnyObject?) -> Void = { [weak self] (paramFromJS) -> Void in
        DispatchQueue.main.async {
            
        }
    }
    context?.setObject(unsafeBitCast(callBack, to: AnyObject.self), forKeyedSubscript: "iosMethod" as NSCopying & NSObjectProtocol)
}

html代码

function btnClick()
{
    iosMethod();
}

在html button点击事件下面加一行iosMethod,然后swift去调用