当浏览器正在获取HTML中的媒体数据时，请使用onprogress 属性执行脚本。
您可以尝试运行以下代码以实现onprogress 属性-
<!DOCTYPE html>
<html>
<body>
<video id = "myVideo" width = "320" height = "176" controls onprogress = "display()">
<source src = "/html5/foo.ogg" type = "video/ogg" />
<source src = "/html5/foo.mp4" type = "video/mp4" />
Your browser does not support HTML5 video.
</video>
<script>
function display() {
alert("Started");
}
</script>
</body>
</html>