如何暂停视频以停止在后台播放？

<video id="myVideo" src="video.mp4"></video>
<button onclick="pauseVideo()">暂停视频</button>

<script>
  function pauseVideo() {
    var video = document.getElementById("myVideo");
    video.pause();
  }
</script>

<video id="myVideo" src="video.mp4"></video>
<button onclick="pauseVideo()">暂停视频</button>

<script>
  function pauseVideo() {
    var video = document.getElementById("myVideo");
    video.pause();
  }
</script>

<video id="myVideo" src="video.mp4"></video>

<script>
  var video = document.getElementById("myVideo");

  document.addEventListener("visibilitychange", function() {
    if (document.visibilityState === "hidden") {
      video.pause();
    } else {
      video.play();
    }
  });
</script>