js倒计时 总结

var countDown = function (){
    var date1 = new Date("2015/4/9"); //目标日期 注意字符串 /格式 -格式IE不支持
    var date2 = new Date();//当前日期
    
    var times = date1.getTime() - date2.getTime();//相差毫秒数
    
    var days = Math.floor(times/(1000*60*60*24)) ///剩余天数
    var rest1 = times%(1000*60*60*24); //取余数
    
    var hours = Math.floor(rest1/(1000*60*60));
    var rest2 = rest1%(1000*60*60);
    
    var minutes = Math.floor(rest2/(1000*60));
    var rest3 = rest2%(1000*60);
    
    var seconds = Math.round(rest3/(1000));///最后秒数四舍五入就可以了
    
    var zero = function (num){
        return num < 10 ? "0" + num : num;
    };
    
    document.body.innerHTML = 
            '倒计时：'
            + days + "天 "
            + zero(hours) + "时 "
            + zero(minutes) + "分 "
            + zero(seconds) + "秒 ";
    
}
countDown();
setInterval(countDown,1000);