videojs改变音量大小

<audio id=example-video preload="auto" class="video-js vjs-default-skin" type="audio/wav" hidden="hidden">
 <script type="text/javascript" th:src="@{/js/jquery3.4.1.js}"></script>
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/video.js/7.6.4/video.min.js"></script>
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/video.js/7.6.4/lang/zh-CN.js"></script>
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/videojs-contrib-hls/5.15.0/videojs-contrib-hls.min.js"></script>
    <script src="https://cdn.bootcss.com/layer/2.3/layer.js"></script>
    <link href="https://cdn.bootcss.com/layer/2.3/skin/layer.css" rel="stylesheet">

<audio id=example-video preload="auto" class="video-js vjs-default-skin" type="audio/wav" hidden="hidden">

<span>音量</span><input type="range" min="10" max="100" id="volume" step="1" value="50"/><span id="volumeLabel">50%</span>

 $("#volume").change(function(){
        var volume = $(this).val();
        $("#volumeLabel").text("x"+volume+"%");
    });

 var player = videojs('example-video');
        player.ready(function() {
            var _this = this
            //速率
            var playbackRate = $("#playbackRate").val();
            var speed = parseFloat(playbackRate);

            var volume = parseFloat($("#volume").val()/100.0);

            setTimeout(function() {
                _this.volume(volume);
               //笔者在测试播放视频控件的demo里发现volume是一个属性，不是函数
            },20);
        });   
...
player.play();