JavaScriptでフルスクリーンウィンドウを作成するにはどうすればよいですか？

JavaScriptでフルスクリーンウィンドウを作成するためのコードは次のとおりです-

例

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
</head>
<style>
   body{
      font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
   }
   button{
      display: block;
      padding:10px;
      margin:10px;
      background-color: rgb(81, 0, 128);
      border:none;
      color:white;
   }
</style>
<body>
<h1>Fullscreen Window with JavaScript Example</h1>
<button class="openVideo";">Open Video in Fullscreen Mode</button>
<video width="500px" controls id="minimizedVideo">
<source
src="https://www.videvo.net/videvo_files/converted/2015_04/preview/Ocean_Waves_slow_motion_videvo.mov44965.webm">
</video>
<h2>Click on the above button to open it in fullscreen</h2>
<script>
   document.querySelector('.openVideo').addEventListener('click',fullscreenVideo);
   var elem = document.getElementById("minimizedVideo");
   function fullscreenVideo() {
      if (elem.requestFullscreen) {
         elem.requestFullscreen();
      }
      else if (elem.mozRequestFullScreen) {
         elem.mozRequestFullScreen();
      }
      else if (elem.webkitRequestFullscreen) {
         elem.webkitRequestFullscreen();
      }
      else if (elem.msRequestFullscreen) {
         elem.msRequestFullscreen();
      }
   }
</script>
</body>
</html>