js实现倒计时效果

第一个效果

js实现倒计时（缺点：到达指定的时间会继续执行倒计时，时间显示的是负数）

<div class="nlpz_sjdjs">剩余：<span>00</span>:<span>00</span>:<span>00</span></div>

<script>
    var starttime = new Date("2017-11-8 19:20:30");
    setInterval(function () {
        var nowtime = new Date();
        //alert(nowtime);
        var time = starttime - nowtime;
        //var day = parseInt(time / 1000 / 60 / 60 / 24);//天
        var hour = parseInt(time / 1000 / 60 / 60 % 24);//小时
        var minute = parseInt(time / 1000 / 60 % 60);//分钟
        var seconds = parseInt(time / 1000 % 60);//秒
        $('.nlpz_sjdjs').html('剩余'+':'+'<span>'+hour+'</span>'+':'+'<span>'+minute+'</span>'+':'+'<span>'+seconds+'</span>');
    }, 1000);
</script>

效果图

第二个效果

js实现倒计时（到达指定的时间会返回一个事件，不会继续执行）

 <div class="nlpz_sjdjs">剩余：<span>00</span>:<span>00</span>:<span>00</span></div>


var starttime = new Date("2017-11-13 16:40:00");
    function tt(){
        var nowtime = new Date();
        //alert(nowtime);
        var time = starttime - nowtime;
        //var day = parseInt(time / 1000 / 60 / 60 / 24);//天
        var hour = parseInt(time / 1000 / 60 / 60 % 24);//小时
        var minute = parseInt(time / 1000 / 60 % 60);//分钟
        var seconds = parseInt(time / 1000 % 60);//秒
        
        if(hour<=0 && minute<=0 && seconds<=0){
            clearInterval(sj);
            $('.nlpz_sjdjs').html("活动已结束");
        }else{
            $('.nlpz_sjdjs').html('剩余'+':'+'<span>'+hour+'</span>'+':'+'<span>'+minute+'</span>'+':'+'<span>'+seconds+'</span>');
        } 
    }
    var sj = setInterval(function () {tt();}, 1000);

效果图（到达确定的时间会返回一个活动结束）

新加时间倒计时

<!doctype html>
<html>

<head>
    <meta charset="utf-8">
    <title>jquery版的网页倒计时效果</title>
    <meta http-equiv="Content-type" content="text/html;charset=UTF-8" />
    <meta content="width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0,user-scalable=no" name="viewport" id="viewport">
    <meta name="format-detection" content="telephone=no" />
    <meta content="yes" name="apple-mobile-web-app-capable" />
    <meta content="black" name="apple-mobile-web-app-status-bar-style" />
    <style type="text/css">
    .time-item strong {
        background: #C71C60;
        color: #fff;
        line-height: 49px;
        font-size: 36px;
        font-family: Arial;
        padding: 0 10px;
        margin-right: 10px;
        border-radius: 5px;
        box-shadow: 1px 1px 3px rgba(0, 0, 0, 0.2);
    }
    
    #day_show {
        float: left;
        line-height: 49px;
        color: #c71c60;
        font-size: 32px;
        margin: 0 10px;
        font-family: Arial, Helvetica, sans-serif;
    }
    
    .item-title .unit {
        background: none;
        line-height: 49px;
        font-size: 24px;
        padding: 0 10px;
        float: left;
    }
    </style>
    <script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js"></script>
    <script type="text/javascript">
    var intDiff = parseInt(30); //倒计时总秒数量

    function timer(intDiff) {
        window.setInterval(function() {
            var day = 0,
                hour = 0,
                minute = 0,
                second = 0; //时间默认值     
            if (intDiff > 0) {
                day = Math.floor(intDiff / (60 * 60 * 24));
                hour = Math.floor(intDiff / (60 * 60)) - (day * 24);
                minute = Math.floor(intDiff / 60) - (day * 24 * 60) - (hour * 60);
                second = Math.floor(intDiff) - (day * 24 * 60 * 60) - (hour * 60 * 60) - (minute * 60);
            }
            if (minute <= 9) minute = '0' + minute;
            if (second <= 9) second = '0' + second;
            $('#day_show').html(day + "天");
            $('#hour_show').html('<s id="h"></s>' + hour + '时');
            $('#minute_show').html('<s></s>' + minute + '分');
            $('#second_show').html('<s></s>' + second + '秒');
            intDiff--;
        }, 1000);
    }

    $(function() {
        timer(intDiff);
    });
    </script>
</head>

<body>
    <div class="time-item">
        <span id="day_show">0天</span>
        <strong id="hour_show">0时</strong>
        <strong id="minute_show">0分</strong>
        <strong id="second_show">0秒</strong>
    </div>
    <!--倒计时模块-->
</body>

</html>