[рони]

sssema96,

<div id="timerAvr"></div>
    <script>
function puskAvr(sec) {
    var timer;
    countdown();
    function countdown() {
        var ar = [sec / 60 | 0, sec % 60].map(function(a) {
            return a.toString().padStart(2, "0");
        }).join(":");
        document.getElementById("timerAvr").innerHTML = "Старт: " + ar;
        sec--;
        if (sec < 0) {
            clearTimeout(timer);
        } else {
            timer = setTimeout(countdown, 1000);
        }
    }
}
puskAvr(90);
    </script>