例子

显示时间到页面上

    <div id="app"></div>
    <script>
        setInterval(show,1000)
        function show() {
            var app = document.getElementById("app")
            var d = new Date();
            var hours = d.getHours();
            var minutes = d.getMinutes();
            var seconds = d.getSeconds();
            var sum = handleNum(hours) + ":" + handleNum(minutes) + ":" + handleNum(seconds);
            console.log(sum)
            app.innerHTML = sum;
        }
        function handleNum(num) {
            if (num < 10) {
                num = "0" + num;
            }
            return num;
        }
    </script>

距离下个时间 多少小时 多少分钟 多少秒

        var time = "2021-10-13 17:10:10"
        /* 多个小时,多分钟,多少秒 */;
        /* 1、获取当前时间的毫秒数 */
        var d = new Date();
        // console.log(d.getTime())
        var startTime = d.getTime();
        /* 2、获取活动开始时间的毫秒 */
        var endTime = new Date(time).getTime();
        // console.log(endTime)
        /* 3、得到中间间隔的毫秒数 */
        var gapTime = endTime -startTime;
        var seconds = Math.floor(gapTime/1000)
        console.log(seconds)
        var hours = Math.floor(seconds/3600);
        console.log(hours)
        seconds = seconds - 3600*hours;
        var minutes = Math.floor(seconds/60);
        console.log(minutes)
        seconds = seconds - minutes*60;
        console.log(seconds)

距离某天还有几天几小时几分

    <script>
        /*  var  time ="2021-10-19 08:30:00" 还有几天几小时几分 */
        var time = "2021-10-19 08:30:00"
        var startTime = (new Date()).getTime();
        var endTime = (new Date(time)).getTime();
        var gapTime = endTime-startTime;
        var minutes = Math.floor(gapTime/(1000*60));
        /* 
        8201分
        1h = 60m
        1t = 60*24
         */
        // console.log(minutes)
        var days =  Math.floor(minutes/(60*24));
        minutes = minutes -days*(60*24)
        console.log(days)
        var hours = Math.floor(minutes/60);
        console.log(hours)
        minutes = minutes - hours*60;
        console.log(minutes)
    </script>