倒计时2（小于0时的格式）

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>倒计时4不用引入插件</title>
    <style type="text/css">
    * {
        margin: 0;
        padding: 0;
    }
    /*倒计时 模块*/

    .count_down {
        overflow: hidden;
        background: #fff;
        padding-bottom: 30px;
    }

    .cd_words {
        color: #fff;
        font-size: 18px;
        text-align: center;
        width: 100%;
        text-shadow: 0 0 2px #000;
        padding-top: 10px;
    }

    .cd_date {
        display: inline-block;
        color: #fff;
        width: 100%;
        box-sizing: border-box;
        padding-top: 5px;
        text-align: center
    }

    .cd_day {
        color: #f7cf93;
        width: 100%;
        text-align: center;
    }

    .cd_day span {
        font-size: 30px;
        color: #fd9800;
        font-weight: 700;
        padding: 0 5px;
        display: inline-block;
    }

    .cd_bottom {
        font-size: 14px;
        background-color: #c51216;
        border-radius: 5px;
        width: 200px;
        height: 40px;
        line-height: 40px;
        margin: 10px auto;
        color: #fff;
        text-align: center;
    }

    .cd_time {
        display: inline-block;
        vertical-align: top;
    }

    .cd_time span {
        background-color: #fff;
        border-radius: 3px;
        color: #6e4200;
        width: 30px;
        height: 30px;
        line-height: 30px;
        text-align: center;
        display: inline-block;
        font-size: 16px;
        margin: 5px 3px 0;
        vertical-align: top;
    }
    </style>
</head>

<body>
    <div class="count_down">
        <p class="cd_day ">还有<span id="t_d ">loading...</span>天</p>
        <div class="cd_bottom ">
            <div class="cd_time "><span id="t_h ">loading...</span>时</div>
            <div class="cd_time "><span id="t_m ">loading...</span>分</div>
            <div class="cd_time "><span id="t_s ">loading...</span>秒</div>
        </div>
    </div>
    <script type="text/javascript ">
    function GetRTime() {
        var timer;
        var EndTime = new Date('2019/02/09 16:46:00');
        var NowTime = new Date();
        var t = EndTime.getTime() - NowTime.getTime();
        //判断活动结束后时间显示为0
        if (t > 0) {
            var d = Math.floor(t / 1000 / 60 / 60 / 24);
            var h = Math.floor(t / 1000 / 60 / 60 % 24);
            var m = Math.floor(t / 1000 / 60 % 60);
            var s = Math.floor(t / 1000 % 60);
            // 小于0的时候，格式00:00:00
            function isZero(num) {
                return num < 10 ? '0' + num : num;

            }

            document.getElementById("t_d ").innerHTML = isZero(d);
            document.getElementById("t_h ").innerHTML = isZero(h);
            document.getElementById("t_m ").innerHTML = isZero(m);
            document.getElementById("t_s ").innerHTML = isZero(s);

        } else {
            document.getElementById("t_d ").innerHTML = '00';
            document.getElementById("t_h ").innerHTML = '00';
            document.getElementById("t_m ").innerHTML = '00';
            document.getElementById("t_s ").innerHTML = '00';
            clearInterval(timer);
        }

    }
    setInterval(GetRTime, 0);
    </script>
</body>

</html>
效果图：