毫秒数转换为指定格式日期的js代码

window.onload = function(){
    var mmsecond = 1111111111111;
    var result = [60,60,24];
    var flag;
    var result_re = "";
    mmsecond = Math.floor(mmsecond/1000);
    //变成秒单位,但是不操作
    var i;
    //下面这个for计算时分秒
    for(i=0;i<3;i++){
        flag = Math.floor(mmsecond%result[i]);
        mmsecond = Math.floor(mmsecond/result[i]);
        if(flag < 10){
            result_re = "0"+flag +":"+ result_re;
        }else{
            result_re = flag +":"+ result_re;
        }
    }
    //去掉最后的一个冒号
    result_re = result_re.substring(0,result_re.length-1);
    //下面计算年月日
    var year,month,day;
    var everyMonth = [31,28,31,30,31,30,31,31,30,31,30,31];
    //计算年
    flag = Math.floor(mmsecond/365);
    year = 1970 - 0 + flag;
    mmsecond = Math.floor(mmsecond%365);
    //计算月和日
    for(i=0;i<12;i++){
    //判断闰月
        if(((year%4 == 0)&&(year%100 != 0)) || (year%400 == 0)){
            if(mmsecond == 59){
                month = "02";
                day = "29";
                break;
            }
        }
        if(mmsecond > everyMonth[i]){
            mmsecond -= everyMonth[i];
        }else{
            month = i+1;
            day = mmsecond;
            month = month >10?month:"0"+month;
            day = day>10?day:"0"+day;
        }
    }
    //拼起来
    result_re = year + "-" + month +"-"+day + " " + result_re;
    alert(result_re);
}