Javascript 如何将JS脚本的flatterweb参数传递到html文件（HTMLElement，iframe）参数？

我想在Flatter web应用程序中渲染一个pay小部件，我需要一个唯一的令牌，所以我从Dart调用Iframe来渲染它。但是，我没有找到如何发送参数或调用dart func（仅关于dart func，但这不起作用）

这里我从iframe给HTMLELEMNT打电话

final html.IFrameElement _iframeElement = html.IFrameElement();
    _iframeElement.height = MediaQuery.of(context).size.height.toString();
    _iframeElement.width = MediaQuery.of(context).size.width.toString();
    _iframeElement.src =
    'paywall.html';
    _iframeElement.style.border = 'none';
    _iframeElement.id = 'iframe';
    final wrapper = html.DivElement()
      ..style.width = '100%'
      ..style.height = '100%';
    wrapper.append(_iframeElement);

    
    // ignore: UNDEFINED_PREFIXED_NAME
    ui.platformViewRegistry.registerViewFactory(
      viewID,
          (int viewId) => wrapper,
    );

    return Scaffold(
        body: SizedBox(
      height: 500,
      child: HtmlElementView(
        viewType: viewID,
      ),
    ));

请帮助我找到一种方法，从颤振Web中传递2个字符串参数的JS调用dart func

String foo() {
    return "ct-2830b393-000f-5000-8000-19466365c438";
  }

  js.context['foo'] = foo;

final html.IFrameElement _iframeElement = html.IFrameElement();
    _iframeElement.height = MediaQuery.of(context).size.height.toString();
    _iframeElement.width = MediaQuery.of(context).size.width.toString();
    _iframeElement.src =
    'paywall.html';
    _iframeElement.style.border = 'none';
    _iframeElement.id = 'iframe';
    final wrapper = html.DivElement()
      ..style.width = '100%'
      ..style.height = '100%';
    wrapper.append(_iframeElement);

    
    // ignore: UNDEFINED_PREFIXED_NAME
    ui.platformViewRegistry.registerViewFactory(
      viewID,
          (int viewId) => wrapper,
    );

    return Scaffold(
        body: SizedBox(
      height: 500,
      child: HtmlElementView(
        viewType: viewID,
      ),
    ));