如何使Internet Explorer在加载页面处于单独的框架中时显示加载状态指示器(旋转圆圈)？

<div class="loader"></div>

<style>
.loader {
  border: 4px solid #f3f3f3;
  border-top: 4px solid #3498db;
  border-radius: 50%;
  width: 20px;
  height: 20px;
  animation: spin 2s linear infinite;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}
</style>

var frame = document.getElementById('your-frame-id');
var loader = document.getElementById('loader-id');

frame.onloadstart = function() {
  loader.style.display = 'block';
};

frame.onload = function() {
  loader.style.display = 'none';
};