js倒计时简单实现方法

function timeDown(second) {  var month = '', day = '', hour = '', minute = '';  if (second >= 86400 * 30) {   month = Math.floor(second / (86400 * 30)) + '月';   second = second % (86400 * 30);  }  if (second >= 86400) {   day = Math.floor(second / 86400) + '天';   second = second % (86400);  }  if (second >= 3600) {   hour = Math.floor(second / 3600) + '小时';   second = second % 3600;  }  if (second >= 60) {   minute = Math.floor(second / 60) + '分';   second = second % 60;  }  if (second > 0) {   second = second ? second + '秒' : '';  }  return month + day + hour + minute + second; }

<!-- 引入jquery --><script> $(function () {  var second = 10000;  $('.remain_time').html(timeDown(second));  setInterval(function () {   second--;   $('.remain_time').html(timeDown(second));  }, 1000); })</script><span class="remain_time"></span>

   $.fn.timeDown = function (opt) {    var second = opt.second;    var tip = '已过期';    var $this = this;    self._timeDown = function (second) {     var month = '', day = '', hour = '', minute = '';     if (second >= 86400 * 30) {      month = Math.floor(second / (86400 * 30)) + '月';      second = second % (86400 * 30);     }     if (second >= 86400) {      day = Math.floor(second / 86400) + '天';      second = second % (86400);     }     if (second >= 3600) {      hour = Math.floor(second / 3600) + '小时';      second = second % 3600;     }     if (second >= 60) {      minute = Math.floor(second / 60) + '分';      second = second % 60;     }     if (second > 0) {      second = second ? second + '秒' : '';     } else {      return tip;     }     return month + day + hour + minute + second;    };    $this.html(self._timeDown(second));    setInterval(function () {     second--;     $this.html(self._timeDown(second));    }, 1000)   };// 使用方式$('.remain_time').timeDown({second:1000,tip:'已过期'})