在iOS中，当用户滚动WKWebView时，如何检测屏幕上可见的html元素？

webView.scrollView.delegate = self

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    webView.evaluateJavaScript("getVisibleElements()") { (result, error) in
        if let elements = result as? [String] {
            // 处理可见的HTML元素
            print(elements)
        }
    }
}

function getVisibleElements() {
    var elements = [];
    var viewportHeight = window.innerHeight;
    var allElements = document.getElementsByTagName("*");
    
    for (var i = 0; i < allElements.length; i++) {
        var element = allElements[i];
        var rect = element.getBoundingClientRect();
        
        if (rect.top < viewportHeight && rect.bottom > 0) {
            elements.push(element.outerHTML);
        }
    }
    
    return elements;
}