尝试更改播放率

Question

我想使用javascript更改视频的播放速度。

这是我的html代码：

//Playback Speeds

const playbackSpeed = document.getElementById("speedButtons"); //Add variable to different speed buttons

playbackSpeed.addEventListener("click", changeSpeed);

function changeSpeed() {
  myVideo.playbackRate = playbackSpeed.buttons[playbackRate.selectedIndex].value;
}

<div id="Speeds">
  <button type="button" id="speedButton">Speed</button>
  <div id="speedButtons">
    <button value=0.5>0.5x</button>
    <button value=0.75>0.75x</button>
    <button value=1>1x</button>
    <button value=1.25>1.25x</button>
    <button value=1.5>1.5x</button>
    <button value=1.75>1.75x</button>
    <button value=2>2x</button>
  </div>

它不起作用。这是我从Chrome浏览器得到的错误：

videoScripts.js:144 Uncaught ReferenceError: playbackRate is not defined
at HTMLDivElement.changeSpeed (videoScripts.js:144)

这就像chrome在谈论的javascript中的144：

playbackSpeed.buttons[playbackRate.selectedIndex].value;