function syncMain() {
    /*
    Gets the shuffle buttons.
    */
    var shuffleButtons = document.getElementsByClassName("amplitude-shuffle");

    /*
    Iterate over all of the shuffle buttons.
    */
    for (var i = 0; i < shuffleButtons.length; i++) {
      /*
      Ensure the shuffle button doesn't belong to a playlist. We have
      a separate method for that.
      */
      if (shuffleButtons[i].getAttribute("data-amplitude-playlist") == null) {
        /*
        If the state of the player is shuffled on, true, then
        we add the 'amplitude-shuffle-on' class and remove the
        'amplitude-shuffle-off' class. If the player is not shuffled
        then we do the opposite.
        */
        if (_config2.default.shuffle_on) {
          shuffleButtons[i].classList.add("amplitude-shuffle-on");
          shuffleButtons[i].classList.remove("amplitude-shuffle-off");
        } else {
          shuffleButtons[i].classList.add("amplitude-shuffle-off");
          shuffleButtons[i].classList.remove("amplitude-shuffle-on");
        }
      }
    }
  }
Syncs the global shuffle button visual state.

@access public