计时 时分秒

<script>
    var hour, minute, second;  //时 分 秒
    hour = minute = second = 0;     //初始化
    var int;

    function p(s) {
        return s < 10 ? '0' + s: s;
    }

    function reset() {
        window.clearInterval(int);
        document.getElementById('timetext').innerHTML = '00:00:00';
        hour = minute = second = 0;
    }

    function start() {
        int = setInterval(timer, 1000);
    }
    //计时
    function timer() {
        second++;
        if(second >= 60) {
            second = 0;
            minute = minute + 1;
        }

        if(minute >= 60) {
            minute = 0;
            hour = hour + 1;
        }
        document.getElementById('timetext').innerHTML = p(hour)+':'+p(minute)+':'+p(second);
    }
</script>