选择日期组件日期-自动计算年龄

思路：

　　1. 利用组件自带的 change事件 获取到字符串 "2019-01-23"  组件查看链接：https://www.antdv.com/components/time-picker-cn/

　　2.把这个字符串 传入到 下面函数；

　　3.打印  returnAge 就是年龄

jsGetAge(strBirthday) {
var returnAge;
var strBirthdayArr = strBirthday.split("-");
var birthYear = strBirthdayArr[0];
var birthMonth = strBirthdayArr[1];
var birthDay = strBirthdayArr[2];
var 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
},