/**

  *  获取几天之前日期

  */

  daysAgo(dayNum = 0) {

     let myDate = new Date()

     let lw = new Date(myDate - 1000 * 60 * 60 * 24 * dayNum) // 最后一个数字多少天前的意思

     let lastY = lw.getFullYear()

     let lastM = lw.getMonth() + 1

     let lastD = lw.getDate()

     let startdate = lastY + "-" + (lastM < 10 ? "0" + lastM : lastM) + "-" + (lastD < 10 ? "0" + lastD : lastD)

     return startdate

 }

 /**

  *  获取几个月之前日期

  */

  monthAgo(monthNum = 0) {

     let newDate = new Date();

     let year = newDate.getFullYear(); //获取当前日期的年份

     let month = newDate.getMonth() + 1; //获取当前日期的月份

     let day = newDate.getDate(); //获取当前日期的日

     let days = new Date(year, month, 0)

     days = days.getDate() //获取当前日期中月的天数

     let year2 = year

     // 进行月份计算

     let month2 = parseInt(month) - monthNum

     if (month2 <= 0) {

         year2 = parseInt(year2) - parseInt(month2 / 12 == 0 ? 1 : Math.abs(parseInt(month2 / 12)) + 1)

         month2 = 12 - (Math.abs(month2) % 12)

     }

     // 进行日期计算

     let day2 = day

     let days2 = new Date(year2, month2, 0)

     days2 = days2.getDate()

     if (day2 > days2) {

         day2 = days2

     }

     let startdate = year2 + "-" + (month2 < 10 ? "0" + month2 : month2) + "-" + (day2 < 10 ? "0" + day2 : day2)

     return startdate

 }

 /**

  *  获取几年之前日期

  */

  yearAgo(yearNum = 0) {

     let newDate = new Date();

     let year = newDate.getFullYear(); //获取当前日期的年份

     let month = newDate.getMonth() + 1; //获取当前日期的月份

     let day = newDate.getDate(); //获取当前日期的日

     let year2 = year - yearNum;

     let startdate = year2 + "-" + (month < 10 ? "0" + month : month) + "-" + (day < 10 ? "0" + day : day)

     return startdate

 }

   /**

    *  根据日期获取上一个月

    */

   preMonth(data) {

     let curMonth = new Date(data)

     let month = curMonth.getMonth() - 1;

     curMonth.setMonth(month);

     let newMonth = curMonth.getMonth() + 1;

     if (newMonth < 10) {

       newMonth = "0" + newMonth;

     }

     return curMonth.getFullYear() + '-' + newMonth;

   }

   /**

    *  获取当前年月(yyyy-MM)

    */

   theCurrentMonth() {

     let date = new Date();

     let nowMonth = date.getMonth() + 1;

     if (nowMonth >= 1 && nowMonth <= 9) {

       nowMonth = "0" + nowMonth;

     }

     let nowDate = date.getFullYear() + '-' + nowMonth;

     return nowDate

   }

   /**

    *  获取上个月第一天

    */

   firstdate() {

     let date = new Date();

     let nowMonth = date.getMonth() + 1;

     if (nowMonth >= 1 && nowMonth <= 9) {

       nowMonth = "0" + nowMonth;

     }

     let nowDate = date.getFullYear() + '-' + nowMonth + '-01';

     return nowDate

   }

  /**

   *  获取上个月最后一天

   */

  enddate() {

    let date = new Date();

    let day = new Date(date.getFullYear(), date.getMonth(), 0).getDate();

    let nowMonth = date.getMonth() + 1;

    if (nowMonth >= 1 && nowMonth <= 9) {

      nowMonth = "0" + nowMonth;

    }

    let nowDate = date.getFullYear() + '-' + nowMonth + '-' + day;

    return nowDate

  }