检测浏览器是否支持html5 <video>标签 javascript

<script type="text/javascript"> 
function checkVideo()
{
if(!!document.createElement('video').canPlayType)
  {
  var vidTest=document.createElement("video");
  oggTest=vidTest.canPlayType('video/ogg; codecs="theora, vorbis"');
  if (!oggTest)
    {
    h264Test=vidTest.canPlayType('video/mp4; codecs="avc1.42E01E, mp4a.40.2"');
    if (!h264Test)
      {
      document.getElementById("checkVideoResult").innerHTML="Sorry. No video support."
      }
    else
      {
      if (h264Test=="probably")
        {
        document.getElementById("checkVideoResult").innerHTML="Yes! Full support!";
        }
      else
        {
        document.getElementById("checkVideoResult").innerHTML="Well. Some support.";
        }
      }
    }
  else
    {
    if (oggTest=="probably")
      {
      document.getElementById("checkVideoResult").innerHTML="Yes! Full support!";
      }
    else
      {
      document.getElementById("checkVideoResult").innerHTML="Well. Some support.";
      }
    }
  }
else
  {
  document.getElementById("checkVideoResult").innerHTML="Sorry. No video support."
  }
}
</script>