页面一旦加载，就开始加载视频 - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
</head>
<body>

  <button onclick="enablePreload()" type="button">加载视频</button>
  <button onclick="disablePreload()" type="button">不加载视频</button>
  <button onclick="checkPreload()" type="button">检查加载状态</button>
  <br>
  <video id="video1" controls="controls">
  <source src="/examples/mov_bbb.mp4" type="video/mp4">
  <source src="/examples/mov_bbb.ogg" type="video/ogg">
  您的浏览器不支持 HTML5 video  标签。
</video>

  <script>
    myVid = document.getElementById("video1");

    function enablePreload() {
      myVid.preload = "auto";
    }

    function disablePreload() {
      myVid.preload = "none";
    }

    function checkPreload() {
      alert(myVid.preload);
    }
  </script>

  <p>Video courtesy of <a href="http://www.bigbuckbunny.org/" target="_blank">Big Buck Bunny</a>.</p>

</body>
</html>
        