Javascript video poster

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  <title>Javascript video poster</title>
  <style>

    .app {
      font-size: 10px;
      z-index: 1;
      text-decoration: none;
      font-family: verdana;
      font-weight: bold;
      color: red;
      position: absolute;
      top: 0;
      right: 0;
      margin: 5px;
      border: 2px solid red;
      padding: 5px 10px;
    }


    body {
      cursor: context-menu;
      margin: 0;
      font-family: calibri;
    }

    #sec {
      border: 5px solid red;
      width: 60%;
      height: calc(60vw / 1.777);
      position: relative;
      margin: 10px auto;
    }

    #vid {
      transform-origin: left top;
      width: 100%;
      position: absolute;
    }

    #poster {
      position: absolute;
      width: 100%;
      height: 100%;
    }

    @media all and (orientation:portrait) {
      #sec {
        border: 0;
        width: 100%;
        height: calc(100vw / 1.777);
        margin: 0;
      }
    }

    @media all and (orientation:landscape) and (max-width:768px) {
      #sec {
        border: 0;
        width: 100%;
        height: calc(100vw / 1.777);
        margin: 0;
      }
    }
  </style>
</head>

<body>
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  <section id='sec'>
    <video id='vid' src='video.mp4' controls></video>
    <img onclick='start()' id='poster' src='poster.jpg' />
  </section>

  <script>
    vid.addEventListener("loadedmetadata", function() {
      x = this.videoWidth;
      y = this.videoHeight;
      videoRatio = x / y;
      boxHeight = getComputedStyle(sec).getPropertyValue("height");
      videoWidth = getComputedStyle(vid).getPropertyValue("width");
      videoHeight = parseFloat(videoWidth) / parseFloat(videoRatio);
      result = parseFloat(boxHeight) / parseFloat(videoHeight);
      vid.style.transform = "scale(1," + result + ")";
    });

    function start() {
      poster.style.display = 'none';
      vid.play();
      vid.style.display = 'block';
    }

     vid.ontimeupdate = () => {
       if(vid.currentTime == vid.duration ){
       poster.style.display = 'block';
       vid.pause();
       vid.currentTime = 0;
       vid.style.display = 'none';
    }
    }


  </script>
</body>
</html>