let configuration = WKWebViewConfiguration()
if let path = NSBundle.mainBundle().pathForResource("customUserScript", ofType: "js"),
source = try? NSString(contentsOfFile: path, encoding: NSUTF8StringEncoding) as String {
let userScript = WKUserScript(source: source, injectionTime: WKUserScriptInjectionTime.AtDocumentStart, forMainFrameOnly: false)
let userContentController = WKUserContentController()
userContentController.addUserScript(userScript)
configuration.userContentController = userContentController
}
let webView = WKWebView(frame: self.view.bounds, configuration: configuration)
Any value in the [WKUserScriptInjectionTime](<https://developer.apple.com/library/ios/documentation/WebKit/Reference/WKUserScript_Ref/index.html#//apple_ref/c/tdef/WKUserScriptInjectionTime>)
enum is valid: .AtDocumentStart
, .AtDocumentEnd