function arrowKeys(e) {
  switch(e.keyCode) {
    case 39:
      var prev = document.getElementById('prev');
      if(prev) prev.click();
    break;
    case 37:
      var next = document.getElementById('next');
      if(next) next.click();
    break;
  }
}
if(document.readyState == 'complete' || document.readyState == 'loaded')
  document.addEventListener('keydown', arrowKeys);
else {
  if(/Chrome/i.test(navigator.userAgent))
    window.addEventListener('load', function () {
      document.addEventListener('keydown', arrowKeys);
    });
  else
    document.addEventListener('DOMContentLoaded', function () {
      document.addEventListener('keydown', arrowKeys);
    });
}
if(x = document.getElementById("player"))
  x.volume = 0.3;