js経典小判例のカウントダウン



<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>     title>
head>
<body>
    <p>    2020      <span>span>p>
    <script>
        var span=document.getElementsByTagName("span")[0];
        var holiday = new Date('2020/10/1');
        var day;//
        var hour;//
        var min;//
        var sec;//
        //                  ,                 
        setInterval(function () {
            var now = new Date();
            var long = holiday.getTime()-now.getTime();//   
            sec=parseInt(long/1000%60);
            min=parseInt(long/1000%3600/60);//   60 
            hour=parseInt(long/1000%(3600*24)/3600);//         ,   3600 
            day=parseInt(long/1000/60/60/24);
            span.innerHTML=day+" "+hour+" "+min+" "+sec+" ";
        },1000)

    script>
body>
html>