【js计算年龄】

[kind-hearted]

function addDays(date, days) {
  var diff = days * 24 * 60 * 60 * 1000;

  return new Date(date.getTime() + diff);
}

function formatYMD(date) {
  var year = date.getFullYear();
  var month = date.getMonth() + 1;
  var day = date.getDate();

  month = month > 9 ? month : '0' + month;
  day = day > 9 ? day : '0' + day;

  return year + '-' + month + '-' + day;
}

// console.log(formatYMD(new Date()) === '2019-01-14');
// console.log(formatYMD(new Date(2018, 0, 9)) === '2018-01-09');
// console.log(formatYMD(addDays(new Date(), 2)) === '2019-01-16');
// console.log(formatYMD(addDays(new Date(), 30)) === '2019-02-13');

function getAgeByYMD(birthday, end) {
	birthday = birthday.split('-');
  end = end.split('-');

  var years = end[0] - birthday[0];
  var diffMonth = end[1] - birthday[1];

  if (diffMonth < 0 || (diffMonth === 0 && (end[2] - birthday[2]) < 0)) {
    years = years - 1;
  }

  return years;
}
console.log(getAgeByYMD('1990-01-01', formatYMD(new Date())) === 29);
console.log(getAgeByYMD('1990-01-14', formatYMD(new Date())) === 29);
console.log(getAgeByYMD('1990-01-15', formatYMD(new Date())) === 28);
console.log(getAgeByYMD('1990-02-15', formatYMD(new Date())) === 28);
console.log(getAgeByYMD('1959-01-14', formatYMD(new Date())) === 60);