JavaScript 网页中实现一个计算当年还剩多少时间的倒数计时程序

function counter() { 
  var date = new Date(); 
  var year = date.getFullYear(); 
  var date2 = new Date(year, 11, 30, 23, 59, 59); 
  /*转换成秒*/ 
  var time = (date2 - date) / 1000; 
  var day = Math.floor(time / (24 * 60 * 60)) 
  var hour = Math.floor(time % (24 * 60 * 60) / (60 * 60)) 
  var minute = Math.floor(time % (24 * 60 * 60) % (60 * 60) / 60); 
  var second = Math.floor(time % (24 * 60 * 60) % (60 * 60) % 60); 
  var str = year + "年还剩" + day + "天" + hour + "时" + minute + "分" + second + "秒"; 
  console.log(str); 
} 
window.setInterval("counter()", 1000); 

var oDateNow = new Date();
var oYear = oDateNow.getFullYear();
var oDateEnd = new Date();
oDateEnd.setFullYear(oYear+1);
oDateEnd.setMonth(0);
oDateEnd.setDate(0);
oDateEnd.setHours(0);
oDateEnd.setMinutes(0);
oDateEnd.setSeconds(0);
function upDate(){
var oDateNow = new Date();
var iTime = oDateEnd.getTime()-oDateNow.getTime();
var iRemain = iTime/1000;
var iDay=parseInt(iRemain/86400);
iRemain%=86400;
var iHour=parseInt(iRemain/3600);
iRemain%=3600;
var iMin=parseInt(iRemain/60);
iRemain%=60;
var iSec=parseInt(iRemain);
document.write(oYear+"年还剩"+iDay+"天"+iHour+"时"+iMin+"分"+iSec+"秒");
}
setInterval(function(){ upDate() },1000);