WKWebView scroll to anchor location useful if having to add header/footers that scroll with it

WKWebView Anchors.swift

@IBOutlet var scrollView: UIScrollView!
var webView: WKWebView!

/// container for the webView in the storyboard
@IBOutlet var webViewContainer: UIView!

/// height of the container
@IBOutlet var webViewHeightConstraint: NSLayoutConstraint!

override func viewDidLoad() {
    super.viewDidLoad()

    webView = WKWebView()
    webView.isOpaque = false
    webView.backgroundColor = UIColor.clear
    webView.scrollView.backgroundColor = UIColor.clear
    webView.navigationDelegate = self
    webView.scrollView.isScrollEnabled = false
    webViewContainer.addSubview(webView)
    webView.autoPinEdgesToSuperviewEdges()
    webView.loadHTMLString(rawHTML, baseURL: nil) // html from your source, file, etc.
}

extension YourViewController: WKNavigationDelegate {

	func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
        if navigationAction.navigationType == .linkActivated,
            let link = navigationAction.request.url?.absoluteString,
            link.starts(with: "about:blank%23") {
            if let anchor = link.replaceMatches(in: "about:blank%23", withFormat: "") {
                    let javascript = "document.getElementById('\(anchor)').offsetTop"
                    self.webView.evaluateJavaScript(javascript) { [weak self] (result, error) in
                        if let offset = result as? CGFloat {
                            self?.scrollView.contentOffset.y = offset
                        }
                }
            }
        }
        decisionHandler(WKNavigationActionPolicy.allow)
    }

    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        var height = max(webView.frame.size.height, webView.scrollView.contentSize.height)

        self.webView.evaluateJavaScript("document.body.offsetHeight", completionHandler: { [weak self] (result, error) in
            // if the document was a PDF result will be nil. Otherwise it'll be the height.
            if let resultAsCGFloat = result as? CGFloat {
                // Need to add a bit to the bottom to prevent clipping
                height = max(height, resultAsCGFloat + 20)
            }									  
            self?.webViewHeightConstraint.constant = height
            self?.webView.setNeedsUpdateConstraints()
        })
    }
}