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length property

Returns the number of tracks in a TextTrackList, TextTrackCueList, or AudioTrackList list object.

This property is read-only.

HTML5 A vocabulary and associated APIs for HTML and XHTML, Section 4.8.10.12

Syntax

JavaScript
numTracks = object.length

Property values

Type: Integer

Number of tracks represented by the list object.

Standards information

HTML5 A vocabulary and associated APIs for HTML and XHTML, Section 4.8.10.12

Remarks

The maximum number of audio tracks a video can contain has not been defined in the World Wide Web Consortium (W3C) specification.

Examples

The following example uses the length property to get the number of audioTracks associated with a video object, and then displays the language and enabled status of each.

HTML



  <script type="text/javascript">                
    function getLanguages() {
      oAudioTracks = document.getElementById("video1").audioTracks;
      document.getElementById("display").innerHTML = "";
      for (var i = 0; i < oAudioTracks.length; i++) {
        document.getElementById("display").innerHTML += "Track " + i + " Language: " + oAudioTracks[i].language + " is   " + ((oAudioTracks[i].enabled == true) ? "enabled" : "not enabled")+"<br/>";
      }
    }      
  </script>
  </head>
  <body>
    <video id="video1" src="multi-lang-movie.mp4" controls >HTML5 video not supported </video>
    <br />
    <button onclick="getLanguages();">Get language status</button>
    <div id="display"></div>
  </body>
</html>

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