代码示例:(标识:event_onprogress_addeventlistener)
<!DOCTYPE html> 
<html> 
<body> 

<p>本例使用 addEventListener() 方法将 "progress" 事件附加到 video 元素。</p>

<video controls id="myVideo">
  <source src="/static/demo/video/shanghai.mp4" type="video/mp4">
  Your browser does not support HTML5 video.
</video>


<script>
document.getElementById("myVideo").addEventListener("progress", myFunction);

function myFunction() {
  alert("Downloading video");
}
</script>

</body> 
</html>
运行结果: