js工具函数：获取传入月份的月初和月末

/**
 * 默认当前月
 * @param date 带月份的日期，例：2021-8
 * @returns 月初至月末数组，例：[2021-8-1, 2021-8-31]
 */
function getMonthSE(date) {
  let nowdays = date ? new Date(date) : new Date();
  let year = nowdays.getFullYear();
  let month = nowdays.getMonth() + 1;
 
  if (month < 10) { month = "0" + month; }
 
  let myDate = new Date(year, month, 0);
 
  let startDate = year + "-" + month + "-01";
  let endDate = year + "-" + month + "-" + myDate.getDate();
 
  return [startDate, endDate];
}