根据年月日计算年龄（周岁）

// JS日期系列：根据出生日期 得到周岁年龄
export function getAge (strBirthday) {
  let returnAge
  const strBirthdayArr = strBirthday.split('-')
  const birthYear = strBirthdayArr[0] * 1
  const birthMonth = strBirthdayArr[1] * 1
  const birthDay = strBirthdayArr[2] * 1

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

  if (nowYear === birthYear) {
    returnAge = 0 // 同年 则为0岁
  } else {
    const ageDiff = nowYear - birthYear // 年之差
    if (ageDiff > 0) {
      if (nowMonth === birthMonth) {
        const dayDiff = nowDay - birthDay // 日之差
        if (dayDiff < 0) {
          returnAge = ageDiff - 1
        } else {
          returnAge = ageDiff
        }
      } else {
        const 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
}