直接上干货：

/**
 * 通过时间戳返回yyyy-MM-dd HH:mm:ss
 * @param timestamp
 * @returns {string}
 */
formartDate(param) {
    var time = new Date(timestamp);
    var y = time.getFullYear();
    var m = time.getMonth()+1;
    var d = time.getDate();
    var h = time.getHours();
    var mm = time.getMinutes();
    var s = time.getSeconds();
    return y+'-'+add0(m)+'-'+add0(d)+' '+add0(h)+':'+add0(mm)+':'+add0(s);
}

function add0(m){
    return m<10?'0'+m:m;
}

/**
 * 通过HH:mm:ss字符串返回时间戳
 * @param time str
 * @returns {string}
 */
function formatTimeStr(timestr) {
    return (new Date(timestr)).getTime()+'';
}

/**
 * 根据年份返回年级
 * 例如2015返回大三
 * @param year
 */
function yearToGrade(year) {
    var chnNumChar = ["一","二","三","四","五","六","七","八","九"];
    var date=new Date;
    var nowYear=date.getFullYear();
    var grade = nowYear-year;
    var nowMonth=date.getMonth()+1;
    if(nowMonth<9){
        grade-=1;
    }
    if(grade>=4){
        return "延毕("+year+"届)";
    }else{
        return "大"+chnNumChar[grade];
    }
}