Wie erstelle ich einen einfachen JavaScript-Countdown-Timer mit und ohne jQuery?

function startTimer(duration, display) {
    var timer = duration, minutes, seconds;
    setInterval(function () {
        minutes = parseInt(timer / 60, 10);
        seconds = parseInt(timer % 60, 10);

        minutes = minutes < 10 ? "0" + minutes : minutes;
        seconds = seconds < 10 ? "0" + seconds : seconds;

        display.textContent = minutes + ":" + seconds;

        if (--timer < 0) {
            timer = duration;
        }
    }, 1000);
}

window.onload = function () {
    var fiveMinutes = 60 * 5,
        display = document.querySelector('#time');
    startTimer(fiveMinutes, display);
};

$(function () {
    var timer = 60 * 5,
        display = $("#time"),
        interval;
    $("#start").click(function () {
        interval = setInterval(function () {
            var minutes = Math.floor(timer / 60),
                seconds = timer % 60;
            minutes = minutes < 10 ? "0" + minutes : minutes;
            seconds = seconds < 10 ? "0" + seconds : seconds;
            display.text(minutes + ":" + seconds);
            timer--;
            if (timer < 0) {
                clearInterval(interval);
                timer = 60 * 5;
            }
        }, 1000);
    });
    $("#stop").click(function () {
        clearInterval(interval);
    });
});