网页倒计时，动态显示"××年还剩××天××时××分××秒"

var target = document.getElementById('target');

function getTimeString(){  // 要计算任意两个日期的时间差只要修改currentDate和currentYearDate的值即可

	var currentDate = new Date();

	var year = currentDate.getFullYear();

	var currentYearDate = new Date(year,11,30,23,59,59); //这里应该写11而不是12，因为Date.getDay()方法返回数值总是比当前月份小1

	var time = (currentYearDate - currentDate) / 1000; //得到距今年底还有多少秒

	var day = Math.floor(time / (24*60*60));

	var hours = Math.floor(time % (24*60*60) / (60*60));

	var minutes = Math.floor(time % (24*60*60) % (60*60) / 60);

	var seconds = Math.floor(time % (24*60*60) % (60*60) % 60);

	var str = year +"年还剩"+ day +"天"+ hours +"小时" + minutes +"分" + seconds +"秒";

	target.innerHTML = str;

}

setInterval(getTimeString,1000);

下面这个方法也行，就是性能不太好

var target = document.getElementById('target');

function getTimeString(){

	var date = new Date();

	var eachMonthDay = [31,28,31,30,31,30,31,31,30,31,30,31];

	if(date.getFullYear() % 4 == 0){

		eachmonthDay[1] = 29;

	}

	var dateString = date.getFullYear() + "年还剩" + (11-date.getMonth()) + "月";

	//计算还剩多少天，以当前月天数为基准

	dateString += eachMonthDay[date.getMonth()] - date.getDate() + "天";

	//计算还剩多少小时，以当天为基准

	dateString += (24 - date.getHours() - 1) + "小时";

	//计算还剩多少分钟，以当前时间为准

	dateString += (60 - date.getMinutes() -1) + "分";

	//计算还剩多少秒，以当前时间为准

	dateString += (60 - date.getSeconds()) + "秒";

	target.innerHTML = dateString;

}

var timer = setInterval(getTimeString,1000);