javascript里面获取当前时间以及与当前时间相差天数的时间

//获取当前时间
function getNowFormatDate() {
    var date = new Date();
    return getFormatDate(date);
}


//获得之前时间，传入参数为相差的天数，如果需要向后的时间，减号改为加好
function getBeforeFormatDate(num){
var date = new Date();
date = date.valueOf() - num*24*60*60*1000;
date = new Date(date);
return getFormatDate(date);
}


//格式化时间
function getFormatDate(date){
    var seperator1 = "-";
    var seperator2 = ":";
    var month = date.getMonth() + 1;
    if (month >= 1 && month <= 9) {
        month = "0" + month;
    }
    //如果位数不足两位，补0
    var strDate =   addstrzero(date.getDate());
    var strHour =   addstrzero(date.getHours());
    var strmin =    addstrzero(date.getMinutes());
    var strseconds =addstrzero(date.getSeconds());
    var currentdate = date.getFullYear() + seperator1 + month + seperator1 + strDate
            + " " + strHour + seperator2 + strmin + seperator2 + strseconds;
    return currentdate;
}


//如果位数不足两位，补0
function addstrzero(num){
if(num >= 0 && num <= 9){
num = "0"+num;
}
return num;
}