-(void)webView:(WKWebView *)webView didCommitNavigation:(null_unspecified WKNavigation *)navigation{

     //获取 当前页URL

     NSString *js = @"document.location.href";

     [self.webView evaluateJavaScript:js completionHandler:^(id _Nullable response, NSError * _Nullable error) {

         NSLog(@"response: %@", response);

     }];

 }

 //这个调用只能放在 finish 里，不然会报JS 异常

 - (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation{

     NSString *js = @"headHide()";

     [self.webView evaluateJavaScript:js completionHandler:^(id _Nullable response, NSError * _Nullable error) {

         NSLog(@"\n error: %@", error);

     }];

 }