vue 獲取字符串日期間的差值

/**
   * 獲取當前日期
   * @returns {string}
   * @Example getNowTime('-')
   */
  getNowTime(str){
    let nowDate = new Date();
    let y = nowDate.getFullYear();
    let m = nowDate.getMonth() + 1 < 10 ? "0" + (nowDate.getMonth() + 1) : nowDate.getMonth() + 1;
    let d = nowDate.getDate() < 10 ? "0" + nowDate.getDate() : nowDate.getDate();
    if(str){
      return y + str + m + str + d;
    }else{
      return y + '年' + m + '月' + d + '日';
    }
  },

  /**
   * 獲取兩個字符串日期間的差值
   * @param startDay
   * @param endDay
   * @Example getDifferentialValForDate('2020-01-05','2020-01-10')
   */
  getDifferentialValForDate(startDay,endDay){
    return Math.abs(parseInt((new Date(endDay).getTime() - new Date(startDay).getTime())/(1000 * 60 * 60 * 24)));
  },

  /**
   * 獲取當前月份
   * @returns {string}
   * @Example getNowMonth('-')
   */
  getNowMonth(str){
    let nowDate = new Date();
    let y = nowDate.getFullYear();
    let m = nowDate.getMonth() + 1 < 10 ? "0" + (nowDate.getMonth() + 1) : nowDate.getMonth() + 1;
    if(str){
      return y + str + m;
    }else{
      return y + '年' + m + '月';
    }
  },

  /**
   * 獲取兩個字符串月份間的差值
   * @param startMonth
   * @param endMonth
   * @Example getDifferentialValForMonth('2020-04','2020-01')
   */
  getDifferentialValForMonth(startMonth,endMonth){
    let startMonths = startMonth.split('-');
    let endMonths = endMonth.split('-');
    return Math.abs((parseInt(startMonths[0]) * 12 + parseInt(startMonths[1])) - (parseInt(endMonths[0]) * 12 + parseInt(endMonths[1])));
  },