题解 | #倒计时#

    function second(second) {
        var j = 24 * 60 * 60,
            day = parseInt(second / j),
            hour = parseInt((second % j) / (60 * 60)),
            min = parseInt(second % j % (60 * 60) / 60),
            second = parseInt(second % j % (60 * 60) % 60);
        return {
            day,
            hour,
            min,
            second,
        };
    }

    function render(second) {
        var day = second.day,
            hour = second.hour,
            min = second.min,
            second = second.second,
            dc = document.querySelector('#jsCountdown').children,
            c = dc[0],
            d = dc[1],
            e = dc[2],
            f = dc[3];
        if (day <= 0) {
            c.classList.add('hide');
        } else {
            c.classList.remove('hide');
            c.innerHTML = +day < 10 ? '0' + day + '天' : day + '天';
        }
        d.innerHTML = +hour < 10 ? '0' + hour + ':' : hour + ':';
        e.innerHTML = +min < 10 ? '0' + min + ':' : min + ':';
        f.innerHTML = +second < 10 ? '0' + second : second;
    }