iOS WKWebView没有显示javascript alert（）对话框

I am having some trouble getting a WKWebView in iOS 8 to display an alert dialog that is called from Javascript. After creating a standard WKWebView and loading an HTML file, I have a button on the page that creates a simple alert with some text. This works in UIWebView and in Google Chrome/Safari, but does not appear to be working in WKWebView. Any help is appreciated.I am having some trouble getting a WKWebView in