JavaScript实现京东秒杀效果

* {
            margin: 0;
            padding: 0;
        }
        
        .box {
            width: 190px;
            height: 270px;
            color: #fff;
            text-align: center;
            margin: 100px auto;
            background-color: #d00;
            padding-top: 40px;
            box-sizing: border-box;
        }
        
        .box>h3 {
            font-size: 26px;
        }
        
        .box>p:nth-of-type(1) {
            color: rgba(255, 255, 255, .5);
            margin-top: 5px;
        }
        
        .box>i {
            display: inline-block;
            margin-top: 5px;
            margin-bottom: 5px;
            font-size: 40px;
        }
        
        .box>.time {
            display: flex;
            justify-content: center;
            margin-top: 10px;
        }
        
        .time>div {
            width: 40px;
            height: 40px;
            background: #333;
            line-height: 40px;
            text-align: center;
            font-weight: 700;
            position: relative;
        }
        
        .time>div::before {
            content: "";
            display: block;
            width: 100%;
            height: 2px;
            background: #d00;
            position: absolute;
            left: 0;
            top: 50%;
            transform: translateY(-50%);
        }
        
        .time>.minute {
            margin: 0 10px;
}

<div class="box">
        <h3>京东秒杀</h3>
        <p>FLASH DEALS</p>
        <i class="iconfont icon-lightningbshandian"></i>
        <p>本场距离结束还剩</p>
        <div class="time">
            <div class="hour">00</div>
            <div class="minute">00</div>
            <div class="second">00</div>
        </div>
 </div>

//1.获取需要操作的元素
const oHour = document.querySelector(".hour");
const oMinute = document.querySelector(".minute");
const oSecond = document.querySelector(".second");
 
//2.处理时间差
 const remDate = new Date("2021-10-28 23:59:59");
 
        setTime(remDate);
 
        //开启定时器
        setInterval(function() {
            setTime(remDate);
        }, 1000);
 
        //为了让用户一进来就看得到效果，而不是先是三个00
        // 我们可以对其进行封装处理
        function setTime(remDate) {
            const obj = getDifferTime(remDate);
            // console.log(obj);
 
            //3.将差值设置给元素
            oHour.innerText = obj.hour;
            oMinute.innerText = obj.minute;
            oSecond.innerText = obj.second;
        }
 
        function getDifferTime(remDate, curDate = new Date()) {
            //1.得到两个时间之间的差值（毫秒）
            const differTime = remDate - curDate;
 
            //2.得到两个时间之间的差值（秒 ）
            const differSecond = differTime / 1000;
 
            //3.利用相差的总秒数 / 每一天的秒数 = 相差的天数
            let day = Math.floor(differSecond / (60 * 60 * 24));
            day = day >= 10 ? day : "0" + day;
 
            //4.利用相差的总秒数 / 小时 % 24
            let hour = Math.floor(differSecond / (60 * 60) % 24);
            hour = hour >= 10 ? hour : "0" + hour;
 
            //5.利用相差的总秒数 / 分钟 % 60
            let minute = Math.floor(differSecond / 60 % 60);
            minute = minute >= 10 ? minute : "0" + minute;
 
            // 6.利用相差的总秒数 % 秒数
            let second = Math.floor(differSecond % 60);
            second = second >= 10 ? second : "0" + second;
 
            return {
                day: day,
                hour: hour,
                minute: minute,
                second: second,
            }
        }