如何在CDN被阻止/不可用的情况下加载本地脚本文件作为后备？

<script src="https://cdn1.example.com/script.js" onerror="loadLocalScript()"></script>
<script src="https://cdn2.example.com/script.js" onerror="loadLocalScript()"></script>
<script>
  function loadLocalScript() {
    var script = document.createElement('script');
    script.src = 'local_script.js';
    document.head.appendChild(script);
  }
</script>

<script src="https://cdn.example.com/script.js?fallback=local_script.js"></script>

// 注册Service Worker
navigator.serviceWorker.register('service-worker.js').then(function(registration) {
  console.log('Service Worker 注册成功');
}).catch(function(error) {
  console.log('Service Worker 注册失败', error);
});

// service-worker.js
self.addEventListener('fetch', function(event) {
  var request = event.request;
  var url = new URL(request.url);

  // 拦截CDN请求
  if (url.origin === 'https://cdn.example.com') {
    event.respondWith(
      fetch('local_script.js')
    );
  }
});