JavaScript 获取当月天数的两种实现方式

function getMonthDay(year, month) {
  let days = new Date(year, month + 1, 0).getDate()
  return days
}

function getDays(year, month) {
   let days = [31,28,31,30,31,30,31,31,30,31,30,31] 
  if ( (year % 4 ===0) && (year % 100 !==0 || year % 400 ===0) ) {
        days[1] = 29
  }
　　return days[month]  
}

<script>
    let date = new Date(2020, 2, 0)
    console.log(date.getDate())
</script>