javascript计算年龄怎么做

function jsGetAge(strBirthday){
  var returnAge;
  // 根据生日计算年龄
  //以下五行是为了获取出生年月日，如果是从身份证上获取需要稍微改变一下
  var strBirthdayArr=strBirthday.split("-");
  var birthYear = strBirthdayArr[0];
  var birthMonth = strBirthdayArr[1];
  var birthDay = strBirthdayArr[2];

  d = new Date();
  var nowYear = d.getFullYear();
  var nowMonth = d.getMonth() + 1;
  var nowDay = d.getDate();

  if(nowYear == birthYear){
    returnAge = 0;//同年 则为0岁
  }
  else{
    var ageDiff = nowYear - birthYear ; //年之差
    if(ageDiff > 0){
      if(nowMonth == birthMonth) {
        var dayDiff = nowDay - birthDay;//日之差
        if(dayDiff < 0)
        {
          returnAge = ageDiff - 1;
        }
        else
        {
          returnAge = ageDiff ;
        }
      }
      else
      {
        var monthDiff = nowMonth - birthMonth;//月之差
        if(monthDiff < 0)
        {
          returnAge = ageDiff - 1;
        }
        else
        {
          returnAge = ageDiff ;
        }
      }
    }
    else
    {
      returnAge = -1;//返回-1 表示出生日期输入错误 晚于今天
    }
  }

  return returnAge;//返回周岁年龄

}

console.log(jsGetAge("1995-09-15"));

26

console.log(jsGetAge("1995-09-25"));

25