timer.swift

    func landingPageWillStartLoading() -> Future<Void, NSError> {
        return Future { complete in
            let js = "document.body.contains(document.getElementById(\"loading\"));"
            let deadline = Date.init(timeIntervalSinceNow: 10)
            
            Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true) { [unowned self] timer in
                if (Date() > deadline) {
                    timer.invalidate()
                    complete(.failure(self.loadInitialPageError))
                }
                
                if !self.webView.isLoading {
                    self.webView.evaluateJavaScript(js) { (result, error) in
                        if error == nil && result.toString() == "0" {
                            timer.invalidate()
                            complete(.success())
                        }
                    }
                }
            }.fire()
        }
    }