跨源iframe中的BroadcastChannel在Safari与Firefox中无法正常工作

场景说明 #

我有两个不同源的站点foo.com和bar.com：

• foo.com通过名为payment-info的BroadcastChannel发送消息
• bar.com嵌入了一个托管在foo.com上的iframe，该iframe订阅payment-info频道，收到消息后通过postMessage转发给父窗口（bar.com）
• bar.com仅监听message事件，调用receiveMessage解析消息

iframe代码（托管于foo.com） #

<html><head><script type="text/javascript">
    (function () {
        const bc = new BroadcastChannel('payment-info');

        bc.addEventListener('message', (m) => {
            const data = JSON.parse(m.data);
            data.channel = 'payment-info';

            if (window.top !== window) {
                window.top.postMessage(JSON.stringify(data), '*');
            }
        });
    })();
</script></head><body></body></html>

bar.com端监听代码 #

window.addEventListener('message', function (message) {
    receiveMessage(message);
});

问题现象 #

该功能仅在Chrome中正常工作，在Safari和Firefox中完全失效。

本地测试代码说明 #

我把本地测试用的三个文件（index.html、iframe.html、index2.html）代码合并到了一处：

• index.html和iframe.html同源
• index2.html属于另一个源
• 注：没有两个不同域名的服务器无法仅通过纯HTML/JS完成真实跨域测试

完整测试代码 #

<!--INDEX CODE-->
<!doctype html>
<html lang="">

<head>
  <meta charset="utf-8">
  <title></title>
  <meta name="description" content="">
  <meta name="viewport" content="width=device-width, initial-scale=1">

  <meta property="og:title" content="">
  <meta property="og:type" content="">
  <meta property="og:url" content="">
  <meta property="og:image" content="">

  <meta name="theme-color" content="#fafafa">
</head>

<body>
<p>index page</p>
<a href="/page.html">link</a>

<script>
  let i = 0;
  const bc = new BroadcastChannel('payment-page');

  function sendItem() {
    i+=1;

    const message = '{"message":"Hello from the new window!"}';
    if (window.opener) window.opener.postMessage(message, '*');

    const data = { message: `Hello from broadcast ${i}` };
    console.log(JSON.stringify(data));

    bc.postMessage(JSON.stringify(data))

    console.log(message)
  }
</script>

<button onclick="sendItem()">send item</button>
</body>

</html>
<!--END OF INDEX CODE-->

<!--IFRAME CODE-->
<html><head><script type="text/javascript">
  (function () {
    const bc = new BroadcastChannel('payment-page');

    console.log('broadcast channel is created', bc)

    bc.addEventListener('message', (m) => {
      console.log('proxy: receive message ', m);

      const data = JSON.parse(m.data);
      data.channel = 'payment-page';

      if (window.top !== window) {
        // Inside iframe. Proxy to top.
        console.log('proxy: send to parent');

        window.top.postMessage(JSON.stringify(data), '*');
      }
    });
  })();
</script></head><body></body></html>
<!--END OF IFRAME-->

<!--INDEX2 CODE-->
<!doctype html>
<html class="no-js" lang="">

<head>
  <meta charset="utf-8">
  <title></title>
  <meta name="description" content="">
  <meta name="viewport" content="width=device-width, initial-scale=1">
</head>

<body>
  <iframe
          width="100"
          height="100"
          src="http://domain-1.com:3000//iframe.html"
  ></iframe>

  <script>
   window.addEventListener('message', function (message) {
      if (message.data && typeof message.data === 'string') {
        console.log(JSON.parse(message.data))
      }
    });
  </script>
</body>

</html>

内容的提问来源于stack exchange，提问作者alejandro