jQuery countdown timer for minutes and seconds

Question

I want create a jquery countdown timer, i tried as the following code but it does not work.what do i do?

DEMO: https://jsfiddle.net/tbosn210/

var interval = setInterval(function() {
    
    var timer2 = $("5:01");
    var timer = timer2.split(':');
    //by parsing integer, I avoid all extra string processing
    var minutes = parseInt(timer[0],10);
    var seconds = parseInt(timer[1],10);
    --seconds;
    minutes = (seconds < 0) ? --minutes : minutes;
    if (minutes < 0) clearInterval(interval);
    seconds = (seconds < 0) ? 59 : seconds;
    seconds = (seconds < 10) ? '0' + seconds : seconds;
    //minutes = (minutes < 10) ?  minutes : minutes;
    $('.countdown').html(minutes + ':' + seconds);
}, 1000);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="countdown"></div>