WKWebview获取内容高度

//页面加载完成之后调用
- (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation {
    WS(weakSelf);
    [webView evaluateJavaScript:@"document.body.offsetHeight;" completionHandler:^(id _Nullable any, NSError * _Nullable error) {

        NSString *heightStr = [NSString stringWithFormat:@"%@",any];

        weakSelf.webHeight = heightStr.floatValue;

}

这样写的话会获得的内容高度要不实际的高度多出来好大一截
[webView evaluateJavaScript:@”document.body.scrollHeight” completionHandler:^(id _Nullable height, NSError * _Nullable error) {
NSLog(@”scrollHeight : %@”,height);
}];