platform/video.videojs/dist/video.es.js
function HtmlTrackElementList() {
    var trackElements = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : [];
    classCallCheck(this, HtmlTrackElementList);

    var list = this; // eslint-disable-line

    if (IS_IE8) {
      list = document.createElement('custom');

      for (var prop in HtmlTrackElementList.prototype) {
        if (prop !== 'constructor') {
          list[prop] = HtmlTrackElementList.prototype[prop];
        }
      }
    }

    list.trackElements_ = [];

    /**
     * @memberof HtmlTrackElementList
     * @member {number} length
     *         The current number of `Track`s in the this Trackist.
     * @instance
     */
    Object.defineProperty(list, 'length', {
      get: function get$$1() {
        return this.trackElements_.length;
      }
    });

    for (var i = 0, length = trackElements.length; i < length; i++) {
      list.addTrackElement_(trackElements[i]);
    }

    if (IS_IE8) {
      return list;
    }
  }
function HtmlTrackElementList() {
    var trackElements = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : [];
    classCallCheck(this, HtmlTrackElementList);

    var list = this; // eslint-disable-line

    if (IS_IE8) {
      list = document.createElement('custom');

      for (var prop in HtmlTrackElementList.prototype) {
        if (prop !== 'constructor') {
          list[prop] = HtmlTrackElementList.prototype[prop];
        }
      }
    }

    list.trackElements_ = [];

    /**
     * @memberof HtmlTrackElementList
     * @member {number} length
     *         The current number of `Track`s in the this Trackist.
     * @instance
     */
    Object.defineProperty(list, 'length', {
      get: function get$$1() {
        return this.trackElements_.length;
      }
    });

    for (var i = 0, length = trackElements.length; i < length; i++) {
      list.addTrackElement_(trackElements[i]);
    }

    if (IS_IE8) {
      return list;
    }
  }
Create an instance of this class.

@param {HtmlTrackElement[]} [tracks=[]]
A list of `HtmlTrackElement` to instantiate the list with.