<span class="js-timeout">2:00</span>

var interval;
  function countdown() {
    clearInterval(interval);
    interval = setInterval( function() {
      var timer = $('.js-timeout').html();
      timer = timer.split(':');
      var minutes = timer[0];
      var seconds = timer[1];
      seconds -= 1;
      if (minutes < 0) return;
      else if (seconds < 0 && minutes != 0) {
          minutes -= 1;
          seconds = 59;
      }
      else if (seconds < 10 && length.seconds != 2) seconds = '0' + seconds;

      $('.js-timeout').html(minutes + ':' + seconds);

      if (minutes == 0 && seconds == 0) clearInterval(interval);
    }, 1000);
  }


  var yetVisited = sessionStorage['visited'];

  if (!yetVisited) {
    sessionStorage['minutesLeft'] = minutes;
    sessionStorage['secondsLeft'] = seconds;
    countdown();
  }
  else {
    $('.js-timeout').html(sessionStorage['minutesLeft']+ ':' + sessionStorage['minutesLeft']);
  }