获取当月的最后一天

const getLastDay = (date: Date) => {
  const dateNow = new Date(date)
  let year = dateNow.getFullYear()
  let month = dateNow.getMonth() + 1
  return new Date(
    new Date(
      `${month < 12 ? year : ++year}-${month === 12 ? 1 : ++month} 00:00`
    ).getTime() - 1
  )
}