function _getAge(birth, deg) {
let year = birth.substr(0, 4)
let month = birth.substr(4, 2)
let day = birth.substr(6, 2)
let d = new Date()
let thisYear = d.getFullYear()
let thisMonth = d.getMonth() + 1
let thisDay = d.getDate()
let diffYear = thisYear - year
if (thisMonth < month) diffYear--
switch (deg) {
case '岁':
return diffYear
break
case '月':
return (thisYear - year) * 12 + thisMonth - month
break
case '天':
default:
let dn = new Date(`${thisYear}-${thisMonth}-${thisDay} 00:00:00`).getTime()
let dp = new Date(`${year}-${month}-${day} 00:00:00`).getTime()
return Math.floor((dn - dp) / (1000 * 24 * 3600))
break
}
}
console.log(_getAge('19881115', '岁'))
console.log(_getAge('19881115', '月'))
console.log(_getAge('19881115', '天'))
