data-dash-is-loading何时触发回调函数？

<div data-dash-is-loading="true"></div>

<script>
  const element = document.querySelector('[data-dash-is-loading]');

  // 监听data-dash-is-loading属性的变化
  const observer = new MutationObserver((mutationsList) => {
    for (let mutation of mutationsList) {
      if (mutation.attributeName === 'data-dash-is-loading') {
        const isLoading = element.getAttribute('data-dash-is-loading') === 'true';
        if (!isLoading) {
          // 数据加载完成，执行回调函数
          handleDataLoaded();
        }
      }
    }
  });

  // 开始监听属性变化
  observer.observe(element, { attributes: true });

  // 数据加载完成时的回调函数
  function handleDataLoaded() {
    console.log('Data loaded!');
    // 执行其他操作...
  }
</script>