vue ＋ vant 时间范围最大不能超过XX小时

this.startDate = '2021-06-01 12:00'
this.endDate = '2021-06-01 18: 00'
// 检查时间段有没有超过XX小时
    checkDate() {
      const { startDate: st, endDate: et } = this
      if (st && et) {
        if (st > et) {
          Toast.fail('开始时间不能大于结束时间')
          this.endDate = ''
        } else {
          const st1 = st.substr(0, 16).split(/-| |:/)
          const et1 = et.substr(0, 16).split(/-| |:/)
          if (st1[0] !== et1[0] || st1[1] !== et1[1] || st1[2] !== et1[2]) {
            Toast.fail('需选择同一天')
            this.endDate = ''
          } else if (et1[3] - st1[3] > XX) {
            Toast.fail('时间段选择不能超过六小时')
            this.endDate = ''
          }
        }
      }
    },