将音频时间转换为MM / SS

Question

我正在使用普通的JavaScript + HTML音频播放器，我想构建一个接口，以MM：SS格式显示音频的当前时间。

document.addEventListener('DOMContentLoaded', function () {
  var a = document.getElementById('mytrack');
  a.addEventListener("loadedmetadata", function() {
    var duration1 = document.getElementById('fullDuration');
    duration1.innerHTML = a.duration;
  }, true);
}, false);

<audio id="mytrack" controls autoplay>
  <source src="https://www57.zippyshare.com/downloadMusic?key=Txf9UxEo&amp;time=" type="audio/mp3" />
</audio>
</br>
<span id="fullDuration">0:00</span>