live downcounter with javascript or jquery

Question

counter that i can change time to remain if i want from db i have a time stamp in table in db that maybe change now i want for example every 30sec check that and if changed my down-counter changing

my js script is:

<script>
    var seconds = 100;
    function secondPassed() {
        var minutes = Math.round((seconds - 30)/60);
        var remainingSeconds = seconds % 60;
        if (remainingSeconds < 10) {
            remainingSeconds = '0' + remainingSeconds;  
        }
        document.getElementById('countdown').innerHTML = minutes + ':' + remainingSeconds;
        if (seconds == 0) {
            clearInterval(countdownTimer);
            document.getElementById('countdown').innerHTML = 'Times Up!';
                document.getElementById('passage_text').disabled = true;

        } else {
            seconds--;
        }
    }

    var countdownTimer = setInterval('secondPassed()', 1000);
    </script> 

Answer 1

Try changing this:

var countdownTimer = setInterval('secondPassed()', 1000);

to this:

var countdownTimer = setInterval(secondPassed, 1000);