javascript - 如何使用 libjass

Question

我正在使用这个例子，但不工作。我应该怎么办 ？？

<video id="video" preload="auto" muted controls style="width: 720px; height: auto">
<source src="./vjs/Ansatsu_Kyoushitsu_2_01_Koisuru-PA-Anbient.mkv" type="video/mkv">
<link href="libjass.css" rel="stylesheet">
<script src="libjass.js"></script>
<script>
    var assLoadedPromise = libjass.ASS.fromUrl(".vjs/en.ass");
    var video = document.querySelector("#video");
    assLoadedPromise.then(function (ass) {
        var renderer = new libjass.renderers.DefaultRenderer(video, ass);
    });
</script>
</video>

返回错误playersub:218 Uncaught ReferenceError: libjass is not defined at playersub:218