timer.js

function countdown(minutes) {
    var seconds = 60;
    var mins = minutes
    function tick() {
        var counter = document.getElementById("timer");
        var current_minutes = mins-1
        seconds--;
        counter.innerHTML =
current_minutes.toString() + ":" + (seconds < 10 ? "0" : "") + String(seconds);
        if( seconds > 0 ) {
            setTimeout(tick, 1000);
        } else {
 
            if(mins > 1){
 
               // countdown(mins-1);   never reach “00″ issue solved:Contributed by Victor Streithorst
               setTimeout(function () { countdown(mins - 1); }, 1000);
 
            }
        }
    }
    tick();
}