daysInMonth (year, month) {
    return /8|3|5|10/.test(month) ? 30 : month === 1 ? (!(year % 4) && year % 100) || !(year % 400) ? 29 : 28 : 31
  }
Alternative get total number of days in month
@param {Number} year
@param {Number} m
@return {Number}