length

Summary

Returns the number of tracks in the list.

Property of apis/audio-video/AudioTrackListapis/audio-video/AudioTrackList

Syntax

Note: This property is read-only.

var result = AudioTrackList.length;

Return Value

Returns an object of type unsigned longunsigned long

Examples

(function () {
    // grab the video element
    var video = document.getElementById("video");

    video.addEventListener("loadeddata", function () {

        // get the audiotracks from the video when it's loaded
        var audioTracks = video.audioTracks;

        var tracksSelection = document.getElementById("tracksSelection");

        // loop through the audio tracks
        for (var i = 0; i < audioTracks.length; i++) {

            // create options for the dropdownlist with the id's
            // and languages of the tracks
            var opt = document.createElement('option');
            opt.value = audioTracks[i].id;
            opt.text = audioTracks[i].language;

            tracksSelection.add(opt);
        }
    });

    tracksSelection.addEventListener("change", function (e) {
        // when the item of the dropdownlist changes
        // grab the id from the selected option
        var audioTracks = video.audioTracks;
        var track = audioTracks.getTrackById(e.currentTarget.value);

        //disable all tracks to prevent them from playing all at once
        for (var i = 0; i < audioTracks.length; i++) {
            audioTracks.enabled = false;
        }

        //set the selected track for the video
        track.enabled = true;
    });
})();

View live example

Related specifications

W3C HTML5 Specification

W3C Editor’s Draft

Attributions

• Microsoft Developer Network: Windows Internet Explorer API reference Article