您需要使用相同页面上执行此操作c $ c> onload 在所有iframe加载后触发的事件如下：

You need to do it on the same page using onload event which fires after all iframes are loaded like this:

// show loading image

window.onload = function(){
  // hide loading image
}

<img id="img" src="images/loader.gif"/></div>

<script>
window.onload = function(){
   document.getElementById('img').style.display = "none";
}
</script>