加载媒体数据时，请使用onloaddata事件执行脚本。您可以尝试运行以下代码来实现onloaddata事件-
视频加载后，以下代码会生成一个警告框-
<!DOCTYPE html>
<html>
<body>
<video controls onloadeddata = "display()">
<source src = "/html5/foo.ogg" type = "video/ogg" />
<source src = "/html5/foo.mp4" type = "video/mp4" />
Your browser does not support the video element.
</video>
<script>
function display() {
alert("Loaded!");
}
</script>
</body>
</html>