1 window.onload = function(){ 2     var uS = 604800;  //后台提供 : 秒 3     var day=hour=minute=second=0, timer; 4     var demo = document.getElementById("demo"); 5     //秒数转为 日:时:分:秒 6     uS==0 || (uS<86400||(day=Math.floor(uS/86400), uS=uS%86400))  7         && uS==0 || (uS<3600||(hour=Math.floor(uS/3600), uS=uS%3600))  8         && uS==0 || (uS<60||(minute=Math.floor(uS/60), uS=uS%60))  9         && uS==0 || (second=uS);10     //计时器一只11     timer = setInterval(function(){12         demo.innerHTML= "还剩 "+day+"天"+hour+"时"+minute+"分"+second+"秒";13         second!=0 ? second-- : 14             (second=59, minute!=0 ? minute-- : 15                 (minute=59, hour!=0 ? hour-- : 16                     (hour=23, day!=0 ? day-- : 17                         (hour=minute=second=0, clearInterval(timer)))));18     },1000);19 }

1 <div id="demo"></div>