使用getDate JavaScript计算每月的天数

function getDaysInMonth() {
  var date = new Date();
  var year = date.getFullYear();
  var month = date.getMonth() + 1;

  switch (month) {
    case 2:
      if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
        return 29;
      } else {
        return 28;
      }
    case 4:
    case 6:
    case 9:
    case 11:
      return 30;
    default:
      return 31;
  }
}

var daysInMonth = getDaysInMonth();
console.log("本月的天数为：" + daysInMonth);