倒时器

.js

  var starttime = new Date("2017/11/20");
  
  setInterval(function () {
    var nowtime = new Date();
    var time = starttime - nowtime; 
    var day = parseInt(time / 1000 / 60 / 60 / 24);
    var hour = parseInt(time / 1000 / 60 / 60 % 24);
    var minute = parseInt(time / 1000 / 60 % 60);
    var seconds = parseInt(time / 1000 % 60);
    $('.timespan').html(day + "天" + hour + "小时" + minute + "分钟" + seconds + "秒");
  }, 1000);