Set UIWebView's background color to document body's background color

UIWebViewBackground.swift

self.webView.rx.didFinishLoad
  .subscribe(onNext: { [weak self] in
    guard let `self` = self else { return }
    let script = "window.getComputedStyle(document.body).backgroundColor;"
    guard let result = self.webView.stringByEvaluatingJavaScript(from: script) else { return }
    let optionalComponents = result
      .components(separatedBy: "(").safe[1]?
      .components(separatedBy: ")").safe[0]?
      .components(separatedBy: ",")
      .map { $0.trimmingCharacters(in: .whitespaces) }
      .compactMap { Float($0) }
      .compactMap { CGFloat($0) }
    guard let components = optionalComponents, components.count >= 3 else { return }
    let red = components[0] / 255
    let green = components[1] / 255
    let blue = components[2] / 255
    let alpha = components.safe[3] ?? 1
    self.view.backgroundColor = UIColor(red: red, green: green, blue: blue, alpha: alpha)
  })
  .disposed(by: self.disposeBag)